Turkey warned Syria again on Tuesday that it would not hesitate to retaliate for any strike on its soil as the country's top military commander visited troops stationed at the reinforced border.

"It has become inevitable for our armed forces to retaliate in kind... as the Syrian administration maintains its aggressive position," Prime Minister Recep Tayyip Erdogan told lawmakers from his ruling Justice and Development Party (AKP).

The rebel Free Syrian Army on Tuesday claimed arresting 13 Hizbullah fighters in the countryside of the Syrian province of Homs, warning that it is capable of teaching Hizbullah a lesson in the heart of Dahiyeh, the party's main stronghold in Lebanon.

“Hizbullah is involved in the current clashes in Syria and its fighters are taking part in the ongoing battles,” Fahd al-Masri, head of the FSA Central Media Department, told MTV.

NATO head Anders Fogh Rasmussen warned Tuesday against the dangers of the conflict in Syria escalating, saying alliance member Turkey had shown commendable restraint in response to shelling of its border area.

"I would like to commend the Turkish government for the restraint it has shown in its response to the completely unacceptable Syrian attacks," Rasmussen said as he went into a two-day NATO defense ministers meeting.

U.N. Secretary General Ban Ki-moon on Tuesday urged the Syrian regime to declare an immediate truce to bring an end to the conflict that he said had left 20,000 dead over the last 19 months.

"It is unbearable for the (Syrian) people to continue like this. That is why I have conveyed to the Syrian government (a) strong message that they should immediately declare a unilateral ceasefire," he said.

Twin suicide bombings hit a Syrian air force compound near Damascus killing dozens of people on Tuesday, monitors said, as rebels took a key town on the road between the capital and second city Aleppo and regime troops stormed a key rebel district of the central city of Homs.

Turkey, meanwhile, again warned Syria it would not hesitate to retaliate for any strike on its soil as the country's top military commander visited troops stationed along the reinforced border.

Turkey's top military commander General Necdet Ozel on Tuesday inspected troops in the southeastern Hatay province near the Syrian border, a day after a Syrian shell landed in a nearby town, local media reported.

Ozel inspected military units in the province and was expected to tour the border region, which has been shuttered over the past week with tanks and anti-aircraft missiles, reported the Anatolia news agency.

Opposition MP Butros Harb revealed on Tuesday that the case of the assassination of MP Gebran Tueni may be referred to the Special Tribunal for Lebanon should the Lebanese judiciary fail to address the matter.

He added: “A lawsuit has been filed against Syrian officers linked to the lawmaker's assassination.”

A suicide attacker detonated a car bomb near a compound of the Syrian intelligence on the outskirts of Damascus on Monday, a Syrian official said.

There were no immediate reports of casualties in the blast in Harasta, a suburb of the nation's capital, said the official, speaking on condition of anonymity because he was not authorized to speak to the media.

Abdel Basset Sayda, the head of the main opposition Syrian National Council, entered the country on Monday for the first time since assuming his post in June, rebel sources said.

Sayda paid a visit to the town of Bab al-Hawa in the northwestern province of Idlib, on the border with Turkey, where he met several leaders of the rebel Free Syrian Army, the sources said.

Violence across Syria has killed more than 32,000 people, most of them civilians, since the outbreak of an anti-regime revolt in March last year, a monitoring group said.

Some 1,000 people have been killed in the past week alone, the Syrian Observatory for Human Rights said, as violence escalates across the country.