The grim benchmark came as President Bashar Assad's regime has scored a series of battlefield successes against the rebels seeking his ouster and international efforts to forge a round of peace talks have stalled. After regaining control of the strategic town of Qusair near the border with Lebanon, regime forces appear set on securing control of the central provinces of Homs and Hama, a linchpin area linking Damascus with regime strongholds on the Mediterranean coast, and Aleppo to the north.
In continued violence, a mortar shell slammed into an area near the runway at the Damascus International Airport Thursday, briefly disrupting flights to and from the Syrian capital, officials said, a few weeks after the government announced it had secured the airport road, which had been targeted by rebels in the past.
The country's transportation minister Mahmoud Ibrahim Said told Syrian TV that a shell fired by "terrorists" struck near a warehouse, breaking its windows and wounding a worker there.
He said the attack delayed the landing of two incoming flights, from Latakia and Kuwait, as well as the takeoff of a Syrian flight to Baghdad. No passengers were harmed and no planes were damaged, he said. The regime refers to rebels as "terrorists."
The Britain-based Syrian Observatory for Human Rights said rebel fighters targeted the airport with homemade rockets.
Rebels also battled regime forces for control of a key military base in the central Hama province after chasing soldiers out and setting fire to installations there, activists said.
Following dawn battles, rebels fighting to topple Assad took control of the base on the northern edge of the town of Morek, which straddles the country's strategic north-south highway leading to Aleppo.
By midday, regime forces shelled the base and sent reinforcements in an apparent attempt to regain control of the key base, said the Britain-based Syrian Observatory for Human Rights.
The Observatory, which has a vast network of Syrian activists on the ground, said the rebels killed six government fighters and seizing ammunition and weapons. Two rebel fighters were killed.
An amateur video posted on Hama activists' Facebook page showed flames rising from the burning compound and the bodies of some of the killed fighters. In the video, fighters celebrated the capturing of the base, calling it one of the "most critical" regime outposts in the region.
The Geneva-based U.N. human rights office said it has documented 92,901 killings between March 2011 and the end of April 2013. But the U.N. high commissioner for human rights, Navi Pillay, said it was impossible to provide an exact number, which could be far higher.
The figure was up from nearly 60,000 through the end of November, recorded in an analysis released in January. Since then, U.N. officials had estimated higher numbers, most recently 80,000. The latest report adds more confirmed killings to the previous time period and an additional 27,000 between December and April.
The conflict in Syria began in March 2011 as largely peaceful protests against Assad's autocratic regime. After a relentless government crackdown on the protests, many Syrians took up arms against the regime, turning the uprising into civil war.
The figures trace the arc of violence, with the average monthly number of documented killings rising from around 1,000 per month in the summer of 2011 to an average of more than 5,000 per month since last July. At its height from July to October 2012, the number of killings rose above 6,000 per month.
"The constant flow of killings continues at shockingly high levels," Pillay said. "This is most likely a minimum casualty figure. The true number of those killed is potentially much higher."
Among the victims were at least 6,561 children, including 1,729 children younger than 10.
"There are also well-documented cases of individual children being tortured and executed, and entire families including babies being massacred - which, along with this devastatingly high death toll, is a terrible reminder of just how vicious this conflict has become," Pillay said.
Her office commissioned San Francisco-based nonprofit Human Rights Data Analysis Group to study eight data sets provided by various groups containing 263,000 reported killings. Those lacking a name, date and location of death were excluded, and some duplicates were found.
"Civilians are bearing the brunt of widespread, violent and often indiscriminate attacks which are devastating whole swaths of major towns and cities, as well as outlying villages," Pillay said.
"Government forces are shelling and launching aerial attacks on urban areas day in and day out," she said. "Opposition forces have also shelled residential areas, albeit using less fire-power, and there have been multiple bombings resulting in casualties in the heart of cities, especially Damascus."
The vast majority of the victims are male, but three-quarters of the reported killings do not indicate a person's age, and the analysis could not differentiate between fighters and non-combatants.
The most documented killings were in rural Damascus, with 17,800 people dead. Next were Homs, with 16,400; Aleppo, 11,900; and Idlib, 10,300.
Heilprin reported from Geneva.