Hundreds more were arrested in Homs and Banias and gunfire and troops were reported in suburbs of Damascus. The Syrian Observatory for Human Rights said at least 400 people had been rounded up in the coastal town of Banias since Saturday, adding to an estimated 7,000 already in detention across the country.

A human rights campaigner in Homs said snipers were deployed in several residential neighbourhoods. "Hundreds have fled from three villages just to the southwest of Homs where tanks had deployed," the campaigner told Reuters.

One man, with a brother in Homs, said the city was terrified by the tanks rolling in and the wave of arrests. "By punishing the whole city, they want people to turn against the protesters," he said.

But activists were equally worried about the silence from other parts of the country, including the southern town of Deraa, epicentre of the seven-week revolt that has left more than 800 dead.

The government has gradually succeeded in shutting down some of the communications networks, including the 3G telephone network and some satellite phones, that have enabled activists to spread news and videos around the country. Diplomats say it has been following advice from Tehran, which used a mix of force and telecommunications savvy to face down its own opposition protest movement two years ago.

Some observers in Damascus have started to fear that the widespread clampdown will quash the protests.

"News is so slow to trickle out and now they have taken down a lot of 3Ginternet and satellite phones, making it impossible for activists to work," said one activist in the capital who did not wish to be named.

Wissam Tarif, executive director of the human rights group Insan, said: "People are not afraid of the operations themselves, but they are afraid of being paralysed logistically. They can't gather, they can't talk to each other – it makes it an uneven game."

Tarif, who is monitoring events from The Hague, added: "The wave of detention since Friday has continued without stop. The number of people disappearing is getting higher. People are being picked out of cars at checkpoints."

As the intimidation campaign continues, Tarif says it was a struggle to keep going.

But he added: "On the other side the question is how long can the regime keep this up? And in how many places? They can't occupy the country forever."

**Katherine Marsh is a pseudonym for a journalist who lives in Damascus