U.N. inspectors in Syria face a race against time to get to the site of an alleged chemical weapons attack to gather vital evidence, but the big question Friday is whether red tape will prevent that.

Since it is not a working day in Syria, government offices are closed and many government officials are off. Syria's heavy bureaucracy may also mire the progress of the international demands for access.

The U.N. team is in Syria to examine previous claims of chemical weapons use at three unrelated sites, so it needs special permission to go to the scene of the latest alleged attack in Ghouta, a rebel stronghold on the outskirts of the capital.

The area, which is contested, appeared to be the target of shelling again Thursday night.

U.N. Secretary-General Ban Ki-moon said Friday that allegations the Syrian regime used chemical weapons should be investigated immediately, adding there was "no time to waste" in getting the team into Ghouta.

He said he had called on the Syrian government to allow the team access and was sending U.N. High Representative for Disarmament Affairs Angela Kane to Damascus to press the case for an urgent investigation.

"I can think of no good reason why any party -- either government or opposition forces -- would decline this opportunity to get to the truth of the matter," Ban said.

In an exclusive interview with CNN's "New Day" anchor Chris Cuomo, U.S. President Barack Obama said preliminary signs point to a "big event of grave concern."

"It is very troublesome," he said. "That starts getting to some core national interests that the United States has, both in terms of us making sure that weapons of mass destruction are not proliferating, as well as needing to protect our allies, our bases in the region."

UK Foreign Secretary William Hague suggested the delay in granting access was suspicious. "It seems that the Assad regime has something to hide," he said.

"This is not something that a humane or civilized world can ignore. Our priority is to make sure the world knows the facts of what has happened, and that means the U.N. team that is in Damascus, only 20 minutes away, being able to get there and to investigate."

Time is of the essence, Hague added, since the evidence will deteriorate "over a matter of days."

However, Russia's Foreign Ministry appeared Friday to accuse the Syrian opposition of blocking U.N. access to the site.

"Signals from the opposition, including those of its readiness to ensure the safety and effective work of U.N. experts on territory controlled by its militants, which is so needed today, are not being heard," it said in a statement.

"This directly contradicts an objective investigation into allegations on possible cases of chemical weapons use in Syria, which is what many countries are calling for and what Russia is calling for."

The ministry earlier said Foreign Minister Sergey Lavrov had called for both the Syrian government and opposition to allow access, in a conversation with U.S. Secretary of State John Kerry.

Bodies of women and children

Anti-regime activist groups in Syria say more than 1,300 people were killed in the attack in Ghouta -- many of them women and children.

Graphic video footage showed rows of bodies without apparent injury, as well as people suffering convulsions or apparently struggling to breathe.

CNN could not immediately verify where or when the videos were recorded, and could not authenticate the number killed or injured.

The images of victims from this incident, including many children, are "heartbreaking and sickening," Ban said.

"Any use of chemical weapons anywhere, by anybody, under any circumstances, would violate international law. Such a crime against humanity should result in serious consequences for the perpetrator."

Ban said the situation in Syria, where rebels have been fighting the forces of President Bashar al-Assad for more than two years, continues to worsen. The death toll has surged past 100,000, he said.

In a statement Friday, European Union foreign policy chief Catherine Ashton backed the United Nations' request for "a thorough, impartial and prompt investigation into these alleged chemical attacks."

"The international community must now urgently show a united face and ensure that a credible and thorough investigation can be carried out," she said.

A million child refugees

Meanwhile, two U.N. agencies said Friday that the number of child refugees from Syria has now passed a landmark threshold, with 1 million forced to flee during the conflict. They make up half of all refugees from the country.

About 740,000 of the children registered are younger than 11, U.N. children's agency UNICEF said. Most have arrived in Lebanon, Jordan, Turkey, Iraq and Egypt, with some families also heading to North Africa and Europe.

"This one millionth child refugee is not just another number," said UNICEF Executive Director Anthony Lake. "This is a real child ripped from home, maybe even from a family, facing horrors we can only begin to comprehend."

Inside Syria, about 7,000 children have been killed during the conflict, according to the Office of the High Commissioner for Human Rights, while another 2 million children have been internally displaced.

U.N. High Commissioner for Human Rights Antonio Guterres told CNN there was the risk of a lost generation in Syria and many of the children caught up in the conflict are showing a high level of trauma.

"I've seen many that do not speak any more, I've seen some with broken sleeping, that have enormous difficulties, some with behaviors that are very challenging and very strange," he said.

The apparent presence of many small children among the victims of Wednesday's alleged attack will add to concerns about the safety of Syria's most vulnerable citizens.

Claims denied

Al-Assad's government has denied any claims it used chemical weapons.

"Everything that has been said is absurd, primitive, illogical and fabricated," Syrian Information Minister Omran Zoabi said on state TV. He said the claim was timed by the opposition to coincide with the U.N team's visit and came as government forces were making gains on all sides against the rebels.

In the streets of government-controlled Damascus, many people said they do not believe the government resorted to the use of nerve agents. The CNN team is in Syria is on an officially approved trip.

"The government would never use chemical weapons because Bashar al-Assad is part of the country, he grew up here, they are Syrians," one man told CNN.

Another said he believed that if anyone was hit, it was members of the rebel Free Syrian Army.

Residents confirmed that there appeared to be a massive military operation under way early Wednesday, with warplanes dropping bombs and artillery firing for hours.

Staff at the Mezzeh University hospital told CNN they received many casualties Wednesday from the area allegedly hit by the attack. But, they said, the casualties showed no signs of having been subjected to chemical agents.

However, experts who have viewed footage purportedly from the scene say it indicates that some form of chemical seemed to have been used.

Geneva talks?

The U.N.-Arab League envoy to Syria, Lakhdar Brahimi, says he believes the recent violence in Ghouta emphasizes the need for a political settlement between the Syrian government and opposition, his spokeswoman Khawla Mattar told CNN on Friday.

"The human loss is unacceptable and we have to do something about getting all parties, particularly the two Syrian sides ... to the Geneva II (peace talks) sooner than later," Mattar said.

A previous meeting of world leaders aimed at taking steps to bring peace to Syria took place in Geneva, Switzerland, just over a year ago. No date has been set for a second Geneva conference, originally expected in June, but Ban said he was working with Kerry and Lavrov to convene it "as soon as possible."

There is no indication when the U.N. inspection team, currently in Damascus, will be able to travel to the site of the alleged attack, Mattar added.

The allegations of chemical weapons use spurred calls Thursday for the United Nations to act.

Turkey's foreign minister, Ahmet Davutoglu, said that "all red lines" have been crossed in Syria and that the United Nations cannot be indecisive about chemical weapons attacks there.

His French counterpart, Laurent Fabius, said force must be used if the claims of chemical weapons use were proved, although he ruled out the use of ground troops.

Their comments came after the U.N. Security Council held a short-notice briefing late Wednesday to discuss the situation. Russia and China -- consistent allies of the Syrian government -- reportedly blocked a formal resolution.

U.S. options

President Barack Obama has directed the U.S. intelligence community to urgently gather additional information to try to assess whether chemical weapons were used Wednesday, State Department spokeswoman Jen Psaki said Thursday.

At this time, she said, the United States is unable to "conclusively determine" chemical weapons use, but is focused on trying to nail down the facts, along with its international partners.

Psaki said, as she has before, that if reports of chemical weapons use prove true, the president has a range of responses available.

Later, a senior defense official told CNN that "the military continues to refine options for Syria to be prepared for whatever the president might request down the line."

U.N. High Commissioner for Human Rights Navi Pillay said the matter is "of utmost urgency" and the "allegations are exceptionally grave."

Pillay urged the government and opposition to allow investigators "to examine the site of the alleged attacks without any delay or obfuscation."

CNN's Frederik Pleitgen reported from Damascus and Laura Smith-Spark wrote in London. CNN's Samira Said, Arkady Irshenko, Alla Eshchenko, Richard Allen Greene and Becky Anderson contributed to this report.