BEIRUT (AP) -- Mortar shells crashed into an outdoor cafe at Damascus University on Thursday, killing at least 10 students in the deadliest of a rising number of mortar attacks in the heart of the Syrian capital.
The strikes have escalated as rebels fighting to topple President Bashar Assad try to enter the city, terrifying civilians whose support the opposition needs to advance its cause.
It was unclear who fired the rounds. The government blamed "terrorists," its blanket term for those fighting Assad's regime. Anti-regime activists accused the regime of staging the attack to turn civilians against the rebels.
Mortar strikes on Damascus are relatively new in Syria's crisis, which began in March 2011 with protests calling for Assad's ouster, then evolved into a civil war. The U.N. says more than 70,000 have been killed in the conflict.
Since last month, mortar shells have hit previously safe parts of the capital with increasing frequency. The near-daily strikes have frightened residents, and many have begun to avoid open areas and put plastic on their windows to help block flying glass from an explosion or shrapnel.
Some shells appear aimed at government targets, such as one of Assad's palaces and the general command of the Syrian army. Others have hit near civilian targets, including the Sheraton Hotel and a soccer stadium, both on the city's west side. Mortar shells also have struck in areas to the east, like the Christian neighborhood of Bab Touma.
Thursday's strike was the deadliest yet.
State-run Al-Ikhbariya TV showed video of the university cafe where blood pooled on tiles and plastic chairs and pens and eyeglasses littered the area. Later video showed people being treated in a hospital, including a woman with white bandages around her head and a man whose back was peppered with shrapnel wounds.
The dining facility belongs to the Faculty of Architecture in Damascus's central Baramkeh district.
State TV said 15 people were killed in the strike, but the official news agency, SANA, put the death toll at 10 and said dozens were wounded. It also reported three other mortar strikes nearby.
The opposition activist group, the Britain-based Syrian Observatory for Human Rights, put the death toll at 13.
Similar mortar attacks on Tuesday killed at least three people and wounded dozens. Six people were killed by mortar shells in different parts of the city on March 11.
"No one anywhere in the world can imagine a more criminal act than this," SANA quoted Amer al-Mardini, the president of the university, as saying. He said he hoped the wounded would heal quickly and "resume their studies as soon as possible."
Anti-regime activists accused the regime of launching the attack to tarnish the opposition's image.
Elizabeth O'Bagy, who studies the Syrian rebels at the Institute for the Study of War, said it was not possible to determine who was behind the attack, but it appeared to fit the regime's pattern of escalation. In other aspects of the war, such as the use of airstrikes or Scud missiles, the regime has gone from trying to target rebels to more indiscriminate attacks on civilians, she said.
"Because of the fact that it does follow regime behavior, it is more likely to be a regime attack," she said, while acknowledging it could also have been a rebel misfire.
Rebels have established footholds in a number of Damascus suburbs but have only been able to push into limited areas in the south and northeast parts of the capital. The government has retained its grip of downtown Damascus, although the mortar strikes have deepened fear among many residents that they will soon see the violence that has damaged many other Syrian cities.
Thursday was not the first time Syria's universities have been targeted. On Jan. 15, twin blasts hit Aleppo University, killing more than 80 people. The opposition said the regime had bombed the university, while the government accused rebels of striking it with rockets.
Also Thursday, Ghassan Hitto, the newly elected prime minister of the main opposition bloc, said he was reviewing candidates for a planned rebel interim government. It will be a service-oriented administration with nine to 12 ministries and will be based inside Syria, Hitto said during a meeting with Syrian expats in Qatar.
In Washington, State Department spokesman Victoria Nuland said the head of the opposition Syrian National Coalition, Mouaz al-Khatib, has decided to continue serving until his six-month term ends in May. Al-Khatib resigned on March 24, citing frustration with the group and its level of international support. The Coalition rejected his resignation.