BEIRUT (AP) ― The United Nations gave a grim new count Wednesday of the human cost of Syria’s civil war, saying the death toll has exceeded 60,000 in 21 months ― far higher than recent estimates by anti-regime activists.

The day’s events illustrated the escalating violence that has made recent months the deadliest of the conflict: As rebels pressed a strategy of attacking airports and pushing the fight closer to President Bashar Assad’s stronghold in Damascus, the government responded with deadly airstrikes on restive areas around the capital.

A missile from a fighter jet hit a gas station in the suburb of Mleiha, killing or wounding dozens of people who were trapped in burning piles of debris, activists said.

Gruesome online video showed incinerated victims ― one still sitting astride a motorcycle ― or bodies torn apart.

“He’s burning! The guy is burning!” an off-camera voice screamed in one video over a flaming corpse.

It was unclear if the government had a military strategy for attacking the gas station. At least one of the wounded wore a military-style vest often used by rebel fighters. Human rights groups and anti-regime activists say Assad’s forces often make little effort to avoid civilian casualties when bombing rebel areas.

Syria’s conflict began in March 2011 with protests calling for political change but has evolved into a full-scale civil war.

As the rebels have grown more organized and effective, seizing territory in the north and establishing footholds around Damascus, the government has stepped up its use of airpower, launching daily airstrikes. The escalating violence has sent the death toll soaring.

The U.N.’s new count of more than 60,000 deaths since the start of the conflict is a third higher than recent estimates by anti-regime activists. One group, the Britain-based Syrian Observatory for Human Rights, says more than 45,000 people have been killed. Other groups have given similar tolls.

“The number of casualties is much higher than we expected, and is truly shocking,” U.N. High Commissioner for Human Rights Navi Pillay said in a statement.

She criticized the government for inflaming the conflict by cracking down on peaceful protests and said rebel groups, too, have killed unjustifiably. Acts by both sides could be considered war crimes, she said.

She also faulted world powers for not finding a way to stop the violence.

“The failure of the international community, in particular the Security Council, to take concrete actions to stop the bloodletting shames us all,” Pillay said. “Collectively, we have fiddled at the edges while Syria burns.”

The U.S. and many European and Arab nations have demanded that Assad step down, while Russia, China and Iran have criticized calls for regime change.

The new death toll was compiled by independent experts commissioned by the U.N. human rights office who compared 147,349 killings reported by seven different sources, including the Syrian government.

After removing duplicates, they had a list of 59,648 individuals killed between the start of the uprising on March 15, 2011, and Nov. 30, 2012. In each case, the victim’s first and last name and the date and location of death were known. Killings in December pushed the number past 60,000, she said.

The total death toll is likely to be even higher because incomplete reports were excluded, and some killing may not have been documented at all.

“There are many names not on the list for people who were quietly shot in the woods,” Pillay’s spokesman Rupert Colville told the Associated Press.

The data did not distinguish among soldiers, rebels or civilians.

It indicated that the pace of killing has accelerated. Monthly death tolls in summer 2011 were around 1,000. A year later, they had reached about 5,000 per month.

Most of the killings were in the province of Homs, followed by the Damascus suburbs, Idlib, Aleppo, Daraa and Hama. At least three-fourths of the victims were male.

Pillay warned that thousands more could die or be injured, and she said the danger could continue even after the war.

“We must not compound the existing disaster by failing to prepare for the inevitable ― and very dangerous ― instability that will occur when the conflict ends,” she said.

The U.N. refugee agency said about 84,000 people fled Syria in December alone, bringing the total number of refugees to about a half-million. Many more are displaced inside Syria.

While no one expects the war to end soon, international sanctions and rebel advances are eroding Assad’s power.

Rebels recently have targeted two pillars of his strength: his control of the skies and his grip on Damascus.

Rebels in northern Syria attacked a government helicopter base near the village of Taftanaz in Idlib province, activists said. Videos posted online showed them blasting targets inside the airport with heavy machine guns mounted on trucks.

All videos appeared genuine and corresponded with other AP reporting on the events.