(CNN) -- Dozens of people were found slain execution-style in bloody Syria Tuesday, yet another grisly act that opposition activists blame squarely on the government.

The corpses were of at least 81 men who were apparently executed. Residents found them in the Queiq River in the town of Bustan Al-Qasr, near Aleppo city, opposition activists said, and they were pulled from the river.

An opposition video -- the authenticity of which couldn't be verified -- showed a long row of men sprawled on the muddy river bank with head wounds. Their hands were tied behind their backs, and some of the bodies showed signs of torture.

Abu Faris, an opposition spokesman in the Aleppo countryside, said the names of 20 of the victims were confirmed by families, who said their relatives were arrested and detained by Air Force Intelligence in Aleppo. The agency is regarded as one of the government's most important and notorious units.

It was the latest report of mass deaths in the Syrian civil war, an all-out battle between President Bashar al-Assad's government and insurgents.

The Syrian unrest started nearly two years ago when the government cracked down on civilians peacefully protesting government policies. The conflict morphed into a civil war.

Today, it is one of the bloodiest conflicts on the planet, claiming, the United Nations says, more than 60,000 deaths.

"The regime adds another massacre to its record while the entire Arab world and the international community keep watching the Syrian misery in silence and complete hypocrisy," the opposition Syrian Observatory for Human Rights said.

In the opposition video, men can be heard shouting "this is unbelievable" and "some were children, children for God's sake."

One middle-aged man can be heard saying, "Tell the world these were not soldiers. They were not fighters. They are human beings. How come they know what the law of gravity is but they don't know anything about human rights."

The opposition groups in Syria have regularly reported massacres by government forces and their allies. Some of the more notorious such reports include incidents in Taftanaz, Houla, Homs, Hama, Tremseh, Daraya, and Halfaya. Bombings in Aleppo and Damascus have resulted in many deaths.

Great migrations

The mass displacement of Syrians, if it continues, may go down as one of the worst in recent history The number of refugees registered with the United Nations jumped by 110,000 in January, bringing the total to just shy of 585,000.

If the masses of refugees awaiting registration are included, the number burgeons to 708,477, the United Nations High Commissioner for Refugees said.

"It's an unrelenting flow," UNHCR spokeswoman Sybella Wilkes said in Geneva, Switzerland. In just the first hour of her workday Tuesday, the number of refugees surged by 4,000 people.

And when Syrians arrive in neighboring countries, they're extremely needy, Wilkes said, because they wait a very long time before fleeing.

"The last thing that Syrians wanted to do was leave their country," she said, adding that it's not unusual for families to be displaced internally six times before finally deciding to leave their home country.

By contrast, Iraqi refugees escaping that country during the U.S.-led invasion fled more quickly, and as a result, often still had some money in their pockets and were in better physical shape.

Syrian refugees turn up with health conditions that, for lack of treatment, require urgent attention, Wilkes said.

More women arrive who are about to give birth, she said. Recently, one woman lost a child at a U.N. station shortly after delivery because she had not received basic prenatal care.

The flow of refugees accelerated markedly in the second half of 2012, Wilkes said.

To put the speed of the current exodus into perspective: Syria has a population of just over 22,000,000. A year ago, the United Nations had registered fewer than 20,000 refugees. Six months ago, the total number rose to 120,000. By December, the number had climbed to 471,000. And now, 585,000.

Jordan, Turkey and Lebanon are harboring the most Syrians, with more than 150,000 each.

"We have in Jordan day shifts and night shifts" to register new refugees, Wilkes said. "In Lebanon, we have double shifts."

U.S. humanitarian aid

President Barack Obama has approved $155 million in humanitarian aid for people in Syria and refugees fleeing the violence.

That brings the aid toll to $365 million, making the United States the largest single donor of humanitarian assistance to Syria.

"I want to speak directly to the people of Syria," Obama said in a statement Tuesday. "This new aid will mean more warm clothing for children and medicine for the elderly; flour and wheat for your families and blankets, boots and stoves for those huddled in damaged buildings. It will mean health care for victims of sexual violence and field hospitals for the wounded. Even as we work to end the violence against you, this aid will help address some of the immediate needs you face each day."

Obama says the U.S. government has imposed sanctions against Syria, worked to isolate the regime, and backed the opposition. The United States and other nations have refrained from intervening militarily in the civil war.

"American aid means food and clean water for millions of Syrians. American aid means medicine and treatment for hundreds of thousands of patients in Damascus, Daraa and Homs. It means immunizations for one million Syrian children. American aid means winter supplies for more than half a million people in Aleppo, Homs and Deir Ezzor. And we're working with allies and partners so that this aid reaches those in need," Obama said.

CNN's Joe Sterling, Ben Brumfield, Salma Abdelaziz and Saad Abedine reported from Atlanta. CNN's Nick Paton Walsh contributed to this report from Beirut, Lebanon.