BEIRUT - At least 24 people were killed on Thursday in violence across Syria, including 10 in the central province of Homs, and as car bombs exploded in Damascus and the northwest city of Idlib, monitors reported.

A suicide bomber detonated an explosives-packed vehicle in a suburb of the capital, wounding 14 people and damaging one of Shiite Islam's holiest shrines, state media and witnesses reported.

State news agency SANA said the vehicle exploded in a garage 50 metres (yards) from the Sayyida Zeinab shrine. There was "substantial damage in the area of the blast," and "the terrorist who carried out the operation was killed."

The Syrian Observatory for Human Rights reported widespread raids by troops later in the capital.

A car bomb in Idlib city targeted a military checkpoint, the Observatory said, adding that a number of soldiers were killed or wounded.

Eight people, including three opposition fighters, were killed in clashes between troops and rebels in the central city of Homs, it said, while also reporting renewed regime shelling of Rastan in the province of the same name and in Daraa in the south.

Two opposition fighters, including Ahmed Bahbouh -- head of the rebel military office in Rastan and a leading dissident -- were killed at the entrances of the rebel-held town, which the regime has been trying to overrun for months.

Troops bombarded Rastan "using helicopters and mortars, killing and wounding a large number of rebel fighters," the watchdog reported.

The Observatory accused UN observers in Syria of "silence," saying that they "do not move until after a city is defeated by regime troops, as happened in Al-Haffe."

That was a reference to a town in Latakia province that was bombarded for eight days before troops moved in.

In the city of Daraa, five people were killed before dawn in the neighbourhood of Tareek al-Sad, which was heavily shelled, the Britain-based Observatory said.

"Government forces have surrounded the neighbourhood of Tareek al-Sad in preparation to storm the area," it said.

Six people, three soldiers, two officers and a girl, were killed in the central province of Hama.

In Damascus province, three civilians were killed by regime forces.

In the northern province of Aleppo, regime forces blockaded the town of Adnan, the Observatory said, noting that the regime forces had stormed the town of Haritan the day before, causing most residents to flee.

The watchdog said at least 77 people were killed across Syria on Wednesday -- 49 civilians, 21 soldiers and seven rebels.

More than 14,400 people have been killed in the 15-month revolt in Syria, the majority of them civilians, according to the Observatory.

The escalation in violence follows an assessment by UN peacekeeping chief Herve Ladsous on Tuesday that Syria was now locked in a civil war, with regime forces having lost control of "large chunks of territory."