Defiant Syrians prepared to rally on Friday under the banner "No to dialogue" with President Bashar al-Assad's regime while hundreds of people fled the flashpoint city of Hama fearing a crackdown on protests.
Facebook group Syrian Revolution 2011 urged "No to dialogue: What dialogue (is possible) when blood has been spilled, while the towns are besieged? The people want the fall of the regime."
It added: "No to dialogue with the assassins, the still-warm blood of the martyrs is calling us. We are legitimacy... dialogue with the regime is useless."
As per most Fridays, activists around Syria are expected to turn out in force after weekly prayers, especially in Hama, a long-standing centre of opposition, despite reports of people fleeing the city
The Syrian Observatory for Human Rights said that about 100 families -- or 1,000 people in total -- had left Hama, where it said Syrian troops had killed 25 civilians since Tuesday.
They were headed for Salamiyah, some 30 kilometres (20 miles) to the southeast.
Syrian authorities have been trying to quell protests in Hama and had positioned tanks on the city's main access routes, except in the north.
Observatory chief Rami Abdel Rahman said two civilians were killed on Thursday in Hama.
"Security forces shot them in the legs and then ran them over in their vehicle. They were fatally injured and died on the way to hospital," he said.
US ambassador Robert Ford visited Hama on Thursday, bringing accusations from the regime that the United States was meddling in Syrian affairs.
A senior US official, speaking on condition of anonymity, said Ambassador Ford visited the tense city to "make contact" with opposition leaders.
"The presence of the US ambassador in Hama without previous permission is obvious proof of the implication of the United States in the ongoing events, and of their attempts to increase (tensions), which damage Syria's security and stability," the foreign ministry said in a statement.
"Syria warns against such irresponsible behaviour and stresses its determination to continue to take all measures that will bring back calm and stability to the country," it added after his visit.
Hama has been a symbol of opposition since the 1982 crackdown on a revolt by the banned Muslim Brotherhood against then-president Hafez al-Assad, father of the present leader, in which some 20,000 people were killed.
The authorities had told demonstrators to avoid any confrontations and clear the streets so residents could go to work and to avoid what it called a "last resort" military operation, according to Al-Watan newspaper.
The newspaper, close to the authorities, also said protesters were calling for the former governor to be reinstated, detained demonstrators to be freed, a pledge that the security forces would not intervene and a guarantee of freedom to demonstrate.
Last Friday, an anti-regime rally brought out half a million people in Hama, according to pro-democracy activists. The security services did not intervene and Assad fired the city's governor the next day.
Residents of Hama and the central city of Homs staged a general strike ahead of Friday demonstrations, according to Abdel Rahman, while on Facebook, the Syrian Revolution 2011 called for the boycotting of businesses that trade with Assad's regime.
"Don't pay for the bullets that are being used to kill us", the group urged its online followers, also calling on activists to march on the Turkish border on July 16 in support of "the refugees, exiles and victims" of the unrest.
Rights groups say that more than 1,300 civilians have been killed and 10,000 people arrested by security forces since mid-March when the anti-government protests erupted.