A Sunni extremist group is claiming responsibility after a suicide attacker detonated a car bomb near a compound of the Syrian intelligence service on the outskirts of Damascus on Monday.

Jabhat al-Nusra claimed responsibility on Tuesday for an attack on the air force intelligence compound in the Damascus suburb of Harasta Monday evening. A statement on a militant website by the group's media arm, Al-Manara al-Bayda, said the bombing aimed "to avenge the killing of Muslims and those who suffered injustice."

There was no immediate word on casualties.

The pro-government Al-Ikhbariya channel said the explosion in the Harasta suburb was followed by armed clashes.

Syrian rebels are increasingly targeting security compounds in Damascus.

The Syrian state run news agency did not report the explosion and there were conflicting reports on how badly the compound was damaged. There were no official reports on casualties, but the pro-government Al-Ikhbariya channel said on Monday the blast was heard across Damascus.

Compound also holds detainees

Syrian rebels are increasingly targeting security compounds and symbols of the regime in and around the capital.

Jabhat al-Nusra said it sent two suicide bombers to hit the compound, which it called " a bastion of tyranny and injustice."

The compound, headed by Maj. Gen. Jamil Hassan, a top Assad security aide, contains prisons where activists say hundreds of people have been held and interrogated by security services during the uprising.

Death toll

The Britain-based Syrian Observatory for Human Rights said it counted 32,079 dead as of Sunday.

Among the dead are 22,980 civilians and civilians-turned fighters, 7,884 members of the Syrian military and 1,215 army defectors fighting alongside the rebels.

The numbers can not be confirmed.

There were fears that detainees inside could have killed or wounded in the blast, said the Britain-based Syrian Observatory for Human Rights, an activist group. It said that so far it could not confirm casualties from its sources on the ground.

On Tuesday, a roadside bomb attached to an electricity pole detonated as a packed commuter bus passed by in the Damascus neighbourhood of al-Zablatani neighbourhood, injuring a civilian, a Syrian official told the AP.

An activist group said the number of people killed in the conflict crossed the threshold of 32,000 over the weekend, and the pace is accelerating.

The Britain-based Syrian Observatory for Human Rights said it counted 32,079 dead as of Sunday — among them 22,980 civilians and civilians-turned fighters, 7,884 members of the Syrian military and 1,215 army defectors fighting alongside the rebels.

In the past week alone, more than 1,200 people were killed, according to the head of the Observatory, Rami Abdul-Rahman, who said he only counts named victims or those whose death is verified by other means, such as amateur video.

Ttwo Syrian rebels told The Associated Press that seven military and intelligence officers belonging to Syria's ruling Alawite minority have defected to Jordan. The rebels said they helped the seven cross into Jordan on Monday, and that the highest-ranking figure among them was an army colonel.

Defections by Alawites, who make up the backbone of Assad's regime, are relatively uncommon. Almost all the defections have been from Syria's Sunni majority, who dominate the rebellion.

Three other Alawite intelligence officials came to Jordan three weeks ago, said the two rebels, who spoke to the AP on condition of anonymity for fear of reprisals from the Assad regime. Jordanian officials declined comment.

NATO offers help as Turkey-Syria exchange artillery

On Tuesday, NATO Secretary-General Anders Fogh Rasmussen backed Turkey's right to defend itself.

"I would add to that that obviously Turkey can rely on NATO solidarity, we have all necessary plans in place to protect and defend Turkey if necessary," he said ahead of a meeting of NATO defence ministers in Brussels. 

'This is not a Syrian-Turkish bilateral issue, it is a humanitarian issue and we think that at the same time it's an issue that should be viewed as a regional security issue'—Turkish Deputy Prime Minister Ali Babacan

Turkey and Syria have exchanged mortar and cannon fire across their common border since errant Syrian shells killed five Turkish civilians last week, sparking fears of a wider regional crisis.

NATO nations expressed solidarity with Turkey after errant Syrian shells killed five Turkish civilians last week. But analysts say the alliance is reluctant to involve itself militarily in another conflict at a time when its main priority is the war in Afghanistan and the handover of responsibility for security to Afghan government forces.

"I do believe that the right way forward in Syria is political solution," said Fogh Rasmussen.

Fogh Rasmussen's comments came as the Dogan agency quoted unidentified military sources as saying that at least 25 additional F-16 fighter jets were deployed at Turkey's Diyarbakir air base in the southeast late Monday.

The Turkish military's chief of staff inspected troops along the border with Syria on Tuesday.

The country's Deputy Prime Minister Ali Babacan also voiced his government's reluctance to face Syria alone.

"Whichever step we take, it will be taken in consultation with our friends and our allies and in agreement with them," he said.

"This is not a Syrian-Turkish bilateral issue, it is a humanitarian issue and we think that at the same time it's an issue that should be viewed as a regional security issue. The Arab League is involved, the Islamic Conference Organization is involved and NATO is a part of it."