BEIRUT 芒鈧珺次元官网网址� Syrian government forces launched a counter-attack against rebels in Damascus on Tuesday, following a rebel suicide car bombing and another insurgent assault earlier in the day in the country's capital, media reports said.

It was the second attempt by rebels in three days to penetrate Damascus' defences.

Rebels have been trying for years to break into the heart of Damascus, at times in conjunction with al-Qaida-linked militants. Al-Qaida-affiliated suicide bombers have been targeting government security installations since the early days of the conflict.

Early on Tuesday, Syrian rebels detonated a car bomb in an eastern neighbourhood of Damascus and launched a renewed attack from the city's opposition-held Jobar neighbourhood, according to the Lebanese militant Hezbollah group. There were no immediate reports on casualty numbers in those attacks.

Hezbollah is heavily invested in defending Syrian President Bashar Assad in his country's civil war. Its military media arm said fighting was underway Tuesday in Jobar, which Syrian government forces had held under siege since 2013.

Syrian state media later said the military responded with airstrikes and artillery fire and that government forces repelled the attack.

Sounds of blasts and artillery fire shook Damascus, and smoke clouded the skies over the eastern Jobar and Qaboun neighbourhoods, where fighting had also broken out on Sunday.

Syria's SANA news agency said government forces encircled the "terrorist groups." It said 15 people were wounded in shelling across the capital.

A rebel blitz spearheaded by Syria's al-Qaida branch shook the eastern parts of Damascus on Sunday, with fighters managing to seize a neighbourhood before pro-government forces pushed them back on Monday. It was the most serious insurgent incursion into Damascus since 2012.

The insurgent gains in Damascus, though short-lived, come against the backdrop of months of steady rebel losses to government forces across Syria. It appeared to be an attempt by al-Qaida's affiliate to mount sophisticated attacks against high-value targets to portray itself as the main force capable of fighting the government.

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Associated Press writer Albert Aji Damascus, Syria, contributed to this report.

Philip Issa, The Associated Press