* Hezbollah says slain commander had been targeted by Israel
* Laqqis fought in Syria's civil war, Hezbollah source says
* Israel denies killing Laqqis; previously unknown group makes claim (Adds funeral)
By Laila Bassam and Dominic Evans
BEIRUT, Dec 4 (Reuters) - A Hezbollah commander who fought in Syria's civil war was shot dead outside his home in Lebanon on Wednesday in a killing which the militant Shi'ite Muslim group blamed on Israel.
Hassan al-Laqqis was shot in the head from close range by a silenced gun as he arrived home at around midnight in the Hadath district of Beirut, a source close to Hezbollah said.
Israel, which fought a 34-day war with Hezbollah in 2006, denied any role in the shooting and hinted that the motive may have been Hezbollah's military support for Syrian President Bashar al-Assad in his war with Sunni Muslim rebels.
A previously unknown group, Ahrar al-Sunna Baalbek brigade, claimed responsibility for the attack in a message on Twitter. The claim could not be verified but the name of the purported group suggested Lebanese Sunni Muslim connections.
Film from the scene shown on Hezbollah's Al Manar television showed two bullet marks in a wall and muddy footprints it said had been left by possibly more than one assailant.
"The Israeli enemy tried to get to our martyr brother several times, in more than one location, but these attempts failed until this repugnant assassination," the group said.
Israel would "bear full responsibility and all the consequences for this heinous crime", it said.
Hezbollah said Laqqis had been with the group since it was set up with Iranian support in the 1980s to fight Israeli troops occupying south Lebanon. His son was killed in the 2006 war with Israel. The source close to Hezbollah said Laqqis had taken part recently in several battles in Syria.
Hundreds of mourners attended Laqqis's funeral in Baalbek, following his grey coffin draped in the yellow Hezbollah flag through the rainswept streets of the Bekaa Valley town.
Some blamed Israel for his death. "We are all (heading) this way if God wants it. We are defeating the Zionist plan. This is a Zionist operation," said Ali Saleh.
But Israel denied involvement. "This has strictly nothing to do with Israel," foreign ministry spokesman Yigal Palmor said.
"Hezbollah has made a fool of itself in the past with these automatic and groundless accusations against Israel ... If they are looking for explanations as to what is happening to them, they should examine their own actions."
Hezbollah also blames Israel for a Damascus car bomb five years ago which killed top commander Imad Moughniyah. It has vowed to avenge Moughniyah's killing at a time of its choice.
The source close to Hezbollah said Wednesday's attack also bore the hallmarks of an Israeli operation, and analyst Charles Lister of IHS Jane's in London said it suggested an element of "professionalism and prior intelligence".
"But what is very clear is that it comes under the context of Hezbollah and its role in Syria," he said. "It was expected that Hezbollah would blame Israel, but that is not necessarily the case."
The open role of Hezbollah fighters in the Syrian civil war and the steady flow of Lebanese Sunnis joining the anti-Assad rebels have fuelled sectarian strife in Lebanon.
Car bombs killed dozens of people in Beirut in August and a twin suicide attack on the Iranian embassy in the Lebanese capital killed at least 25 people last month.
An Iranian foreign ministry spokeswoman blamed Israel for that attack, but responsibility was claimed by a Lebanon-based al Qaeda-linked group, the Abdullah Azzam brigades.
Hezbollah leader Sayyed Hassan Nasrallah said he believed the group had support from Saudi Arabia, Iran's main regional rival whose backing for Assad's foes has pushed it deeper into a proxy conflict in Syria against Tehran.
Abdullah Azzam "is not a fictitious name," Nasrallah said in an interview broadcast on Lebanese television on Tuesday night. "This group exists ... It has its leadership ... and I am convinced it is linked to Saudi intelligence," he said.
"Saudi Arabia is the one who runs these kinds of groups in several places in the world." (Additional reporting by Oliver Holmes in Beirut, Reuters TV in Baalbek, Lebanon and Crispian Balmer in Jerusalem; Editing by Alistair Lyon)