BEIRUT (AP) -- Syrians are being killed at an average rate of 5,000 per month, the U.N. said Thursday as it raised the overall death toll in the civil war to nearly 93,000, with civilians bearing the brunt of the attacks.
The grim estimate reflects the growing sectarian nature of the bloodshed as the regime of President Bashar Assad scores a series of battlefield successes against the rebels.
The toll also is a reminder of the international community's helplessness in the face of a conflict that has displaced several million people and spilled over into neighboring countries with alarming frequency.
Adding to the pressure for international action, the United States announced Thursday it had conclusive evidence that Assad's regime has used chemical weapons, including the nerve agent sarin, on a small scale against opposition forces. The White House said multiple chemical attacks last year killed up to 150 people.
Three U.S. officials said President Barack Obama has authorized sending weapons to Syrian rebels for the first time. Obama has said the use of chemical weapons cross a "red line" triggering greater U.S involvement in the crisis.
The U.S. officials said the administration could provide the rebels with a range of weapons, including small arms, ammunition, assault rifles and a variety of anti-tank weaponry such as shoulder-fired remote-propelled grenades and other missiles. However, no final decisions have been made on the type of weaponry or when it would reach the rebels, according to the officials, who insisted on anonymity in order to discuss internal administration discussions.
In the latest violence, a mortar round slammed into an area near the runway at Damascus International Airport, briefly disrupting flights to and from the Syrian capital, officials said. The attack Thursday came a few weeks after the government announced it had secured the airport road that had been targeted by rebels in the past.
It was the first known attack to hit inside the airport, located south of the capital, and highlighted the difficulty Assad faces in maintaining security even in areas firmly under his control.
In Geneva, the U.N. human rights office said it had documented 92,901 killings in Syria 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 began in 2011 as largely peaceful protests of Assad's autocratic regime. After a relentless government crackdown on the demonstrators, many Syrians took up arms against the regime, and the uprising became a civil war.
The conflict now includes Lebanon's Hezbollah and Iranian fighters supporting Assad's armed forces, and al-Qaida-linked extremists backing the opposition.
The government has gained momentum since recapturing the strategic town of Qusair near the border with Lebanon. Regime forces now 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.
Most of the armed rebels in Syria are from the country's Sunni majority, while Assad has retained core support among the minorities, including his own Alawite sect, an offshoot of Shiite Islam.
The international community has been unable to end the violence and a date for a peace conference proposed by the U.S. and Russia weeks ago has been shelved.
Obama and his national security team are "greatly concerned" by the worsening situation in Syria, White House spokesman Jay Carney said, speaking hours before the White House announced there was evidence that the Assad regime had used chemical weapons.
Carney said he expects Syria will be discussed at the Group of Eight summit next week in Northern Ireland.
State Department spokeswoman Jen Psaki said the U.S. was saddened at the latest U.N. estimate, "but we're not shocked."
She said Assad "has used indiscriminate and disproportionate force against Syrian civilians and inflicted unthinkable suffering upon his own people."
The Britain-based Syrian Observatory for Human Rights, which has its own count based on a network of activists around the country, said 98,416 people have been killed from the start of the uprising until Wednesday, many of them members of the military or pro-regime militiamen.