FALLUJA, Iraq, Nov 29 (Reuters) - Gunmen in several cars shot dead an influential Sunni Muslim scholar outside his mosque in the city of Falluja on Tuesday, witnesses said.

Hamza Abbas al-Issawi, a mufti or senior Islamic authority, was coming out of the Wihda mosque after evening prayers when gunmen pulled up near him and opened fire.

"It is shocking, everyone in Falluja knows him, he is very respected," said Safah Naji, a witness.

"Even all the insurgents know him and everyone liked him."

Falluja is a former stronghold of the insurgency and is overwhelmingly Sunni Arab.

The attack follows the killing of other senior Sunni Arab leaders in the past two days. Politicians Iyad Alizi and Ali Hussein, members of the Iraqi Islamic Party, were shot dead as they drove through Baghdad on Monday.

Tit-for-tat killings of Sunnis and Shi'ites have risen dramatically in recent months as the divisions between Iraq's two major Muslim sects deepen.

Some Sunni leaders blame the deaths on Shi'ite militias allied to the government who have infiltrated Iraq's security forces and act with impunity. The Shi'ite-led government denies the existence of such "death squads".

The killing of Issawi is surprising largely because Falluja is so dominated by Sunni Arabs, whether close to the insurgency or not, that it would be difficult for any Shi'ites to penetrate the city and carry out an assassination without quick detection.