Syrian protesters have hurled stones and set roadblocks of burning tyres against government forces trying to enter a key opposition city, nearly a week after a massive protest against the regime of President Bashar Assad, activists said.
Earlier, dozens of families fled the central city of Hama fearing a full-scale crackdown by Assad's troops.
The central Syrian city has become a centre of resistance in the four-month-old uprising and poses a potential dilemma for Assad's government.
A major offensive could make the city a fresh rallying cry for the opposition, but Assad's regime also does not want a repeat of last Friday's stunning rally, when an estimated 300,000 people protested.
In a bid to show solidarity with the residents, US ambassador to Syria Robert Ford visited Hama on Thursday to witness the situation first hand. The State Department stressed he travelled there independently, and not as part of a trip organised by the Syrian government.
Hama also holds deeper symbolism for opposition to the rule of the Assad family. In 1982, the late Hafez Assad ordered troops to crush a rebellion by Islamist forces, killing between 10,000 and 25,000 people, rights activists say.
The Syrian regime has used a mix of fierce violence and promises of reform to try to quell the uprising. Some 1,400 people and 350 members of security forces have been killed since demonstrations began, activists say.
Some of those fleeing Hama, who mostly live on the edge of the city, headed westward to the town of Salamiyeh about 20 miles away, said Rami Abdul-Rahman of the Syrian Observatory for Human Rights and a Hama-based activist.
"They are afraid of military operations in the area," said Abdul-Rahman. Security forces have been conducting arrest raids on Hama's outskirts for the past two days.
Security forces withdrew from Hama last month after a fierce crackdown on demonstrators that killed some 65 people - apparently hoping to appease angry, grieving families. But anti-Assad protests swelled. Last week's outpouring was the largest protest since the mutiny against Assad's regime began in mid-March.