Syrian forces strafed the city of Rastan in central Homs province with machinegun fire from sunrise on Tuesday, wounding at least 20 people, a human rights group said.
The city, about 180 kilometres (120 miles) from Damascus and a gateway to the country's north, has been the focus of security force operations against anti-regime dissent for several days, according to activists.
"At least 20 people were wounded, seven seriously, when soldiers using heavy machine guns on tanks began to open fire at sunrise in Rastan," the Britain-based Syrian Observatory for Human Rights said in a statement.
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"Loud explosions were also heard in the city," it added.
The Local Coordination Committees, which organise protests on the ground, for its part reported a "massive deployment" of security forces at Rastan.
The Observatory, meanwhile, also reported witnesses as saying that sustained automatic gunfire was heard on Tuesday morning at Talbisseh, 10 kilometres south of Rastan.
The office of the UN High Commissioner for Human Rights in Geneva has said the death toll from the crackdown on dissent since March 15 has risen to more than 2,700.