Activists say security forces are conducting mass arrests in Deraa Tanks are heading for the central Syrian city of Homs, local activists say, after anti-government protests were held there last night. Some 1,000 people chanted slogans in support of the southern city of Deraa, where troops are rounding up hundreds of men in house-to-house raids.
Around the country, 2,843 people are confirmed as detained. Campaigners say the total could be 8,000 and that some have been subjected to torture.
The US calls the crackdown "barbaric".
Rights groups say about 560 people have been killed across the country in protests against the repressive rule of President Bashar al-Assad.
The government says that the demonstrators are militant criminals and not - as evidence from the ground suggests - ordinary civilians calling for political reform.
The protests, which began on 15 March, pose the most serious challenge to four decades of rule by the Assad family in one of the Arab world's most repressive and tightly controlled countries.
Foreign journalists are barred from Syria, and reports cannot be verified.
Cities under siege Activists in Homs have told the BBC that security forces had fanned out inside the city, and that army tanks were heading towards it.
The deployment in Homs comes a day after Syrian tanks and troops reportedly surrounded the nearby coastal city of Baniyas.
Deraa, the southern city where the protests kicked off in mid-March, has been under siege since the weekend.
On Wednesday, there were fresh reports of gunfire and more arrests of men aged between 15 and 40. More than 800 protesters have so far been rounded up in Deraa alone.
The army is still not allowing anyone into the city, and supplies of food and medicine are running low, residents say. Communication lines are still down, but electricity has been restored in most areas, they add.
On Tuesday, US state department spokesman Mark Toner said the use of tanks, arbitrary arrests and power cuts in Deraa was "quite barbaric and amounts to the collective punishment of innocent civilians".
The authorities say they have found rebel arms caches in Deraa. But the protesters insist their movement is entirely peaceful.
Despite the government crackdown, Syrians are continuing to protest in several cities and towns.
In the capital, students at Damascus University staged a sit-in at the faculty of economics.
They have issued a statement condemning "the massacres, killings and the arrests committed against peaceful demonstrators."
Torture allegations On Tuesday, a late-night demonstration by 1,000 students at Aleppo University - in Syria's second city - was broken up by security forces using tear gas and firing live bullets, reliable sources say.
No injuries were reported, but dozens of students are being arrested, their mobile phones and laptops confiscated, the sources say.
More vigils and protests are planned in the coming days. Amnesty International, and many of the protesters themselves, say the detainees are subjected to beatings and torture.
"The use of unwarranted lethal force, arbitrary detention and torture appear to be the desperate actions of a government that is intolerant of dissent and must be halted immediately," Amnesty official Philip Luther said. WWW.DOMINICANFLASH.COM
Last week hundreds of members of Mr Assad's ruling Baath Party resigned in protest at the crackdown. European nations have called for sanctions against the regime of President Assad. Washington has already tightened its sanctions against senior Syrian officials.