Syrian activists called countrywide protests on Tuesday in solidarity with thousands of anti-regime activists rounded up by the security forces, setting the scene for another round of bloody clashes.

The call by the Syrian Revolution 2011, an Internet-based opposition group, comes as the European Union listed the younger brother of President Bashar al-Assad among 13 Syrian officials facing sanctions for their involvement in violently repressing pro-democracy demonstrations that first erupted March 15.

"Demonstrations will continue every day," said the Syrian Revolution 2011 Facebook page, which has been a motor of the protests.

It called for "a Tuesday of solidarity with prisoners of conscience held in the jails of the criminal Syrian regime."

Street demonstrations are persistently dispersed with violence by the security forces, who also make mass arrests, according to rights activists, who say more than 600 people have been killed and 8,000 jailed or gone missing in the eight-week crackdown.

In the latest security force bid to crush the anti-regime protest movement, troops went house to house in the coastal city of Banias on Monday, rounding up thousands of men, activists said.

Rami Abdul Rahman, head of the London-based Syrian Observatory for Human Rights, said water, electricity and telephone lines were cut off in Banias, on Syria's northwest Mediterranean coast.

"Thousands of men, including youths, have been rounded up by the army and security forces... to be interrogated and they are being beaten. More than 400 are still being held," he said.

Abdul Rahman told AFP "residents hoped that the army would arrest regime supporters who have terrorised Banias but instead the army arrested unarmed residents."

Among those detained were protest leaders and doctors at a hospital which was encircled by the military, according to the Syrian Observatory.

Several protesters were also arrested Monday night in the city centre of Damascus where some 200 rallied calling for "lifting the siege" imposed on several cities and "an end to the shootings," the Syrian Observatory said.

The military said six soldiers, including three officers, were killed in clashes Sunday as the army pursued "armed terrorist groups" in Banias, Homs and the countryside around the southern town of Daraa -- three protest hubs.

Tanks rumbled into several districts of the central industrial city of Homs and deployed along the corniche in Banias overnight Saturday-Sunday, activists said.

"Banias is cut off from the outside world," one activist said.

In response to the heavy-handed crackdown on dissent, world powers have been mulling a range of measures against the regime and key figures, although they have so far not aimed directly at Assad.

On Tuesday, the EU however put the president's brother, Maher al-Assad, 43, head of the Republican Guard, on top of a list of 13 Syrian officials facing sanctions.

Assad was described as the prime mover of repression against anti-government protesters on the list published in the EU's Official Journal.

He came ahead of General Ali Mamluk, 65, and the new Interior Minister Mohammed Ibrahim al-Shaar, appointed on April 28.

The EU on Monday formally adopted measures including visa bans and assets freeze targeting Syrian officials deemed responsible for the regime's savage crackdown without identifying them.

The United States has warned it would take "additional steps" against Syria if it continues its deadly crackdown.

A Syrian senior government official said in an interview with the New York Times, meanwhile, that she believes Assad's embattled government has ridden out the worst of the uprising.

"I hope we are witnessing the end of the story," Bouthaina Shaaban, an adviser to President Assad who often serves as a spokeswoman, told the US paper in an hour long interview.

"I think now we've passed the most dangerous moment. I hope so, I think so," Shaaban said giving a glimpse at the mindset of a 40-year-old regime that has barred most foreign journalists from Syria since the beginning of the uprising.

"We want to use what happened to Syria as an opportunity," Shaaban added. "We see it as an opportunity to try to move forward on many levels, especially the political level."

The Times reporter was allowed in the country for a few hours, the report added.

Assad, quoted on Monday in pro-government Al-Watan newspaper, vowed to press ahead with reforms and forecast the political crisis in Syria was nearing an end.

"The crisis will pass and end, and the question of administrative, political and press reforms will advance," Assad was quoted as telling a delegation of residents the main port city of Latakia, north of Banias.

In New York, UN deputy spokesman Farhan Haq said Syria blocked a fact-finding team from visiting the southern protest hub of Daraa. "The humanitarian assessment mission has not been able to get into Daraa," he said.

"We are trying to clarify why it hasn't had access."

The Committee of the Martyrs of the 15 March Revolution puts the death toll since March 15 at 708 while the Observatory says 621 civilians were killed and 120 soldiers and security forces.