Dubai: At least six people were killed, including a young girl, as Syrian forces on Tuesday launched a major assault on Herak, a town in the southern province of Daraa.

The girl was shot dead by a sniper, while at least five soldiers were killed in clashes with members of the rebel Free Syrian Army (FSA), the Syrian Observatory for Human Rights said.

"Large military forces, including tanks and armoured troop carriers, launched an assault on Herak. Explosions and heavy machine gun fire were heard," the Britain-based monitoring group added, citing residents.

A video posted online by activists shows what it said was the inside of the Abu Bakr Al Saddiq mosque in Herak. The video showed rubble littering the mosque's entrance, doors blown from their frames and shattered glass covering the floor. An unidentified man says a tank fired on the mosque after residents sought refuge there.

Across the country, 21 people were killed on Tuesday, including 13 from two families in the Baba Amr area of the central city of Homs, the Local Coordination Committees of Syria said on its website.

President Bashar Al Assad vowed yesterday to press ahead with his campaign to crush "terrorism".

"The Syrian people ... have again proven their capacity to defend the nation and to build a new Syria through their determination to pursue reforms along with the fight against foreign-backed terrorism," he said, quoted by state news agency Sana.

Meanwhile, European governments are discussing whether to expel Syrian ambassadors. France's ambassador to Damascus was returning to Paris yesterday after closing down the embassy in Syria.

Turkish Prime Minister Recep Tayyip Erdogan called for an "immediate opening" of humanitarian aid corridors in Syria.