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A radical Lebanese Sunni Muslim cleric said Monday a car bombing in a Beirut stronghold of Hezbollah was "a natural result" of the Shiite group's involvement in Syria's war.

At least 27 people were killed in the bombing last Thursday that targeted the Rweiss neighbourhood, a densely populated mostly-Shiite district in Beirut's southern suburbs.

"The bombing in the southern suburbs of Beirut was a natural result of the crimes committed by (Hezbollah chief Hassan) Nasrallah, his party and supporters against our brothers in Syria, in Qusayr," Sheikh Ahmad al-Assir said, according to an audio recording attributed to him.

Assir has been on the run since clashes between his backers and the Lebanese army in the southern city of Sidon in June that killed at least 18 soldiers.

He gained notoriety for his fierce opposition to Hezbollah, particularly following the group's decision to back the Syrian regime in the country's civil war.

Hezbollah fighters played a key role in the Syrian government's recapture of the rebel bastion of Qusayr, near the Lebanese border, in June.

The group is a key supporter of President Bashar al-Assad and has sent fighters across the border to Syria this year to bolster regime forces which have been battling an uprising since March 2011.

A defiant Nasrallah said on Friday that he himself was ready to go and fight in Syria, and accused radical Sunni "takfiri" Muslims of being responsible for the car bombing.

Assir called the Shiite movement's chief "Nasr Al-Lat," one of the three main pre-Islamic Arabian goddesses of Mecca.

"Nasrallah exploited the bombing to threaten all Lebanese and Sunnis in particular in his recent speech in order to order to give approval to further dominate Lebanon," Assir said.

"He does not want to be held responsible for the crimes he committed against his own people, the Shiites in Lebanon, and the adventure he involved as well as the crimes against the Syrian people, Lebanon and the Sunnis."

Assir added that Nasrallah's use of the term takfiri Muslims "sought to intimidate the Lebanese into staying away from Sunni Islam."

Hezbollah has been criticised for his involvement in Syria's conflict by Lebanese President Michel Sleiman, a Christian Maronite, the majority of Sunni leaders and Hezbollah's rivals in Lebanon.

Lebanon is deeply divided into supporters and opponents of the regime in neighbouring Syria and the conflict now in its third year has stoked sectarian tensions and violence in the country.

"Enough lies, the mask has fallen," Assir said, warning Nasrallah "will use the intelligence and security services that he controls... to fight you under the pretext of (fighting) takfiri Muslims."

Assir said Nasrallah would also use the Lebanese army, describing him as "a fool for standing by the butcher against victims in Syria," and urging Shiites to "stand firm against him."

The recording is Assir's third since he went on the run from Lebanese security forces in June.