Syrian troops have shelled a southern village and clashed with army defectors holed up inside in violence that killed a 15-year-old boy and five government soldiers, activists said.
The clashes in Hirak were some of the worst lately in Daraa province, birthplace of the uprising to oust president Bashar Assad.
Explosions shook the village as shells slammed into residential areas suspected of sheltering defectors. Even mosques were targeted, activists said.
"The clashes are very intense and have been going on since the morning," said Rami Abdul-Rahman, director of the British-based Syrian Observatory for Human Rights, which relies on a network of activists on the ground.
The operation in Daraa began days after Syrian forces captured a key rebel-held neighbourhood in central Homs province, another opposition stronghold. Government troops intensely shelled Homs for four weeks before they captured the Baba Amr neighbourhood in the city, wresting it from rebels who had held it for months.
Activists said hundreds were killed in the month-long offensive.
The assault on Homs was accompanied by a steady rise in international demands for Assad to stop the bloodshed and give up power immediately. On Monday, US senator John McCain called for air strikes against Syria, saying the United States had a moral and strategic obligation to force out Assad and his loyalists.
The US administration has said Assad must got but has said it will not intervene militarily.
A video posted online by activists today shows what it said was the inside of the Abu Bakr al-Saddiq mosque in Hirak. The video showed rubble littering the mosque's entryway, doors blown from their frames and shattered glass covering the floor.
An unidentified man on camera says a tank fired on the mosque after town residents sought refuge there.
Another video shows men, women and children fleeing a building after it appears to be hit by a shell. Heavy automatic gunfire is heard in the background.
A third video shows a man with a deep gash in this thigh that the video says was caused by shrapnel from a tank shell.
Mr Abdul-Rahman said the army was fighting a large number of army defectors in Hirak.
He said the rebels ambushed an armoured personnel carrier, killing five soldiers and wounding several. He and the Local Co-ordination Committees, another activist group, said a 15-year-old boy was killed by snipers.
Security forces were conducting raids in pursuit of defectors and activists, making arbitrary arrests and burning homes, the LCC said. The group reported at least 21 deaths across Syria today.