BEIRUT, Lebanon -- Mortar shells crashed into Umayyad Square in the center of Damascus, the Syrian capital, on Monday, killing at least one person, state media reported, in some of the worst shelling in the heart of the city since the uprising against President Bashar al-Assad began two years ago.
Umayyad Square is a large open space at the center of a major downtown crossroads, less than a mile from the presidential palace. A year ago, it was the scene of a large demonstration in support of President Assad.
Around the square are the state television offices, the army's general staff headquarters, university buildings, the Sheraton hotel, and the Damascus Opera House, a showpiece of the commitment to high culture that Mr. Assad liked to project and the venue for his rare public speech in January. Some state media said as many as six were killed and dozens wounded.
The rebellious Free Syrian Army took responsibility for the attack, saying it used rocket launchers aimed at the state broadcaster.
Shelling in such central areas panicked residents who fear that Damascus, which has largely been spared the urban warfare that has devastated Syria's other major cities, could be next. But so far, the government has managed to keep rebels from pushing deep into the capital.
After mortar shells fell Sunday and Monday near the downtown Damascus hotel that the United Nations uses as its Syria headquarters, the world body told its 800 Syrian employees to work from home for the time being, and evacuated half of its 100 non-Syrian employees to Beirut or Cairo, according to Martin Nesirky, the spokesman for Secretary-General Ban Ki-Moon. Mr. Nesirky said the steps were temporary and should not affect the distribution of humanitarian aid coordinated by the United Nations in Syria.
Opposition groups reported that a senior rebel leader was wounded in an explosion in the town of Mayadeen in eastern Syria where rebels have recently seized large amounts of territory from the government. The leader was Col. Riad al-Assad, one of the most prominent defectors from the Syrian military and a top figure in the Free Syrian Army, the umbrella group that has attempted to unify rebel fighters under a single command.
Colonel Assad has been less prominent in the opposition lately, since another defector, Gen. Salim Idris, was named head of the Free Syrian Army's unified command, which has struggled to unite fighters who largely rely on their individual contacts to obtain weapons. But he still occasionally visits rebel groups inside the country.
It was unclear who was responsible for the explosion that injured Colonel Assad. Some fighters have expressed worry that there could be conflict between battalions that are nominally loyal to the Western-backed Free Syrian Army and battalions that fight under the banner of Islamist groups like the Nusra Front.
Malek al-Kurdi, the deputy commander of the Free Syrian Army, accused the Syrian regime of being involved in the attack on Colonel Assad. Mr. Kurdi said in a telephone interview that an explosive device attached to Colonel Assad's car had detonated after the colonel visited a school in the Mayadeen-Deir al-Zour area, parts of which are still under government control. He said the colonel was treated in a field hospital and then transported to a hospital in Turkey, and that his right leg was amputated below the knee.
Moaz al-Khatib, the president of the opposition coalition, reported on his Facebook page that Colonel Assad was transported to safety with the help of other rebel groups -- a statement that appeared to suggest he had not been attacked by fellow fighters.
"All the battalions operating in the area secured a way to get commander Riad Assaad out of Deir Ezzor which he was visiting," Mr. Khatib wrote, using different transliterations for the names of the colonel and the town. "He was injured and is still alive and we ask God for his safety."
Adding to the murky picture of rebel leadership, Mr. Khatib announced his resignation as coalition president on Sunday, only to have his resignation rejected by the coalition. In Damascus, the Syrian state news agency, SANA, said that six people were killed when a mortar round struck close to the opera house in Damascus. State television, by contrast, said that one person was killed. The military retaliated by shelling rebel positions from Mount Qasioun, where the presidential palace overlooks the city.
It was hard to pinpoint the source of the rebel mortar fire. Reuters reported that insurgents were firing from Kafr Souseh, where rebels have recently attacked security buildings; that area is less than a mile from Umayyad Square.
Heavy artillery strikes by the government were reported in numerous rebel-held suburban towns ringing the city, from Harasta in the northeast to Moadhamiya in the south.
Hania Mourtada and Hwaida Saad contributed reporting from Beirut, and Neil MacFarquhar contributed from the United Nations. _
This article originally appeared in The New York Times.