BEIRUT: Fierce clashes between Syrian regime forces and armed rebels in the central city of Rastan on Monday left at least 23 soldiers dead and dozens wounded, the Syrian Observatory for Human Rights said.

The Britain-based monitoring group said initial reports indicated that three troop carriers were destroyed in the clashes that began at dawn on the outskirts of the rebel-held city, located in Homs province.

A lieutenant who had defected was also killed in the clashes.

Regime forces launched an offensive on Rastan at the weekend but met with sharp resistance from rebels seeking the ouster of the regime of President Bashar al-Assad.

The Observatory said dozens had been wounded in shelling of the city by Syrian troops. The bombardment by regime forces resumed following the deadly clashes, it added.

In Quraya in the eastern province of Deir Ezzor, a 15-year-old boy was killed by machinegun fire as regime forces raided the town, the Observatory said, bringing the total number of people killed on Monday to 25.

The watchdog added that 15 residents of the city were arrested.

And in the capital Damascus, regime forces raided the neighborhood of Qaboon, while snipers were stationed on the roofs of some buildings.

The watchdog said 45 people — 25 civilians, 15 soldiers and five rebels — were killed in a surge of violence in various flashpoints on Sunday, despite a ceasefire brokered by UN-Arab League peace envoy Kofi Annan that was supposed to take effect on April 12.

Among the dead were a Shiite imam, Sheikh Abbas al-Laham, who leads the prayers in the Ruqayya mosque in Damascus, a revered place of pilgrimage for many religious Iranians. The cleric was assassinated by unidentified gunmen in Damascus, the Observatory said.

Iran supports the Damascus regime, which since 15 March 2011 has faced an unprecedented popular revolt.

More than 12,000 people, the majority of them civilians, have died since the Syrian uprising began in March 2011, according to the watchdog, including more than 900 killed since the April 12 truce.