Syrian army shells crashed into southern Damascus on Wednesday and helicopters fired rockets and machineguns during an assault to shore up President Bashar al-Assad's grip on the capital, opposition activists said.
The army has used tanks and helicopter gunships this week in an offensive around Damascus that has coincided with the departure of U.N. military observers after a failed mission to stop the bloodshed and nudge Syria toward a peaceful transition.
Anti-Assad activists said at least 47 people had been killed in Damascus in what they called the heaviest bombardment this month. "The whole of Damascus is shaking with the sound of shelling," said a woman in Kfar Souseh, one of several districts hit during the military offensive to root out rebel fighters.
At least 22 people were killed in Kfar Souseh and 25 in the nearby district of Nahr Eisha, activists said. One of the dead was named as Mohammad Saeed al Odeh, a journalist employed at a state-run newspaper who was sympathetic to the anti-Assad revolt. Activists said he had been executed in Nahr Eisha.
"There are 22 tanks in Kfar Souseh now and behind each one there are at least 30 soldiers. They are raiding houses and executing men," an opposition activist in Kfar Souseh, who gave his name only as Bassam, told Reuters by Skype.
More than 250 people, including 171 civilians, were killed across Syria on Tuesday, mostly around Damascus, Aleppo and the southern city of Deraa, according to the Syrian Observatory for Human Rights, a British-based opposition monitoring group.
Activists in the southwestern Damascus suburb of Mouadamiya said Assad's forces had killed 86 people there since Monday, half of them by execution. It was not possible to verify that report.
There was no immediate government account of the latest fighting. But state television broadcast footage of weapons it said had been seized from rebels in Mouadamiya, which was one of the first districts to join the uprising.
The death toll from the fighting in the northern Lebanese city of Tripoli rose to at least 10 with more than 100 wounded, medical sources said, in what residents said were some of the fiercest clashes there since Lebanon's 1975-90 civil war.
In Syria, Assad's forces have lost swathes of territory in recent months, but have fought back hard in Damascus and in Aleppo, the country's biggest city and commercial hub until it became a theatre for urban warfare.
Reuters journalists in Aleppo heard gunfire and shells exploding every minute. Rebel fighters trying to advance in Saif al-Dawla, a front-line Aleppo district, encountered mortar and rocket-propelled grenade barrages. At one point, their escape route was cut off by gunfire as tank shells exploded nearby.
Much of the area was destroyed. Water poured from one building into the street below. State television said government forces were pursuing "the remnants of armed terrorist gangs".
Syrian government forces also fought rebels on Wednesday for control of a military base and airfield near the eastern town of Albu Kamal on the Iraqi border, according to a local Iraqi official and a Syrian rebel commander.
Opposition sources said Syrian state forces had evacuated two security installations at Albu Kamal on the Iraqi border on Tuesday as rebels made gains after a week of heavy fighting.
They identified the installations as belonging to the Airforce Intelligence and Political Security agencies in Albu Kamal, 120 km (75 miles) southeast of the city of Deir al-Zor.
The rebel commander, known as Abu Khalid, said his forces now controlled Albu Kamal, straddling a supply route from Iraq where many Sunni tribes sympathise with their Syrian kin fighting Assad's forces.