Syrian security services deployed in force in Damascus ahead of mass Friday protests called in support of Homs after a deadly crackdown on dissent in the central city, rights activists said.

"Elements of the army and security forces are deployed in the districts of Qabun and Rukneddin. Barricades were set up at the entrances, limiting exits and entries," said Rami Abdel Rahman of the Syrian Observatory for Human Rights.

Political upheaval in Syria, hit by months of opposition protests, is weighing heavily on neighboring Lebanon where it risks sparking inter-religious clashes, U.N. Special Coordinator for Lebanon Michael Williams warned Thursday.

"There is a great worry in Lebanon about this," said Williams, who raised the potential for "confessional clashes in Lebanon."

Syrian security forces shot dead two people on Thursday as they pressed their clampdown on dissidents in the central city of Homs, the capital and elsewhere, activists said, calling for mass protests.

"There was heavy gunfire in the al-Khalidiyeh, Baba Amr and al-Nazhine quarters (of Homs), and two people were killed," said Abdul Karim Rihawi, head of the Syrian League for Human Rights.

Syria's security forces Thursday pressed a clampdown against dissidents in the central city of Homs, where shots were heard, arrests were made and many streets were deserted, rights activists said.

"(Security forces) entered houses and made arrests," said Rami Abdel Rahman of the London-based Syrian Observatory for Human Rights, reached by telephone.

Syria has apologized to Qatar for an attack by demonstrators on its embassy in Damascus that prompted it to suspend work in the strife-torn country, an official in Doha said on Wednesday.

"Syria has sent a letter of apology to the Qatari ministry of foreign affairs," the Qatari official said on condition of anonymity.

Syrian Foreign Minister Walid Muallem warned the French and U.S. ambassadors on Wednesday not to travel outside Damascus without permission from the authorities, after they both visited the flashpoint central city of Hama earlier this month.

"We will impose a ban on any (diplomatic) travel more than 25 kilometers outside Damascus, if the ambassadors continue to ignore (our) guidance," Muallem told the envoys at a meeting broadcast by state television.

The March 14 general-secretariat hinted on Wednesday that national dialogue became useless after the Syria-Hizbullah alliance decided on behalf of the Lebanese to prevent the state from owning arms.

“Dialogue became useless after three years of time wasting and after the regional-local axis decided on behalf of the Lebanese what their state should not possess,” the general-secretariat said following its weekly meeting.

Progressive Socialist Party leader MP Walid Jumblat announced on Wednesday that Lebanon is committed to the Special Tribunal for Lebanon’s decisions, adding however that this does not mean that foreign meddling in Lebanon is permitted.

He made his statements after holding talks with Russian Foreign Minister Sergei Lavrov during his ongoing visit to Russia.

Al-Mustaqbal parliamentary bloc has tasked MP Mohammed al-Hajjar with questioning the cabinet on the mystery over the release of the seven Estonian tourists last Thursday.

Al-Liwaa daily said Wednesday that al-Hajjar would be the first MP to question Premier Najib Miqati’s cabinet on the issue through parliament.

The head of the Loyalty to the Resistance bloc MP Mohammed Raad stated on Tuesday that the government advocated the “equation of victory of the army, people, and Resistance.”

He added: “The enemy and its masters want to target the Resistance because it represents what is left of dignity in this world.”