Lebanon announced a Saudi pledge of $3 billion on Sunday to buy military equipment from France, as it buried leading Sunni politician Mohammad Chatah, killed in a Beirut car bombing.

Friday's killing of Chatah, a prominent critic of the Syrian regime, revived painful memories of political assassinations and came as the conflict in Lebanon's larger neighbour stoked sectarian tensions.

Saudi Arabia is a leading backer of the rebels battling to overthrow Syrian President Bashar al-Assad, who enjoy widespread sympathy among Lebanese Sunnis.

Lebanon's Shiite Hezbollah movement and its backer Iran are Assad's main regional allies.

Saudi Arabia "decided to provide generous assistance to Lebanon in the form of $3 billion for the Lebanese army to strengthen its capabilities," President Michel Sleiman announced, adding that it was the largest assistance provided in Lebanon's history.

French President Francois Hollande, on a visit to Saudi Arabia, said his country would "meet" any requests from Lebanon.

"I am in touch with President Sleiman... If requests are addressed to us, we will meet them," Hollande told reporters.

Sleiman, who visited Saudi Arabia last month, said the money would be used to buy weapons from France, pointing to the "depth of the military cooperation" between Lebanon and its former colonial ruler.

Lebanon's armed forces are woefully under-equipped and face multiplying security challenges, underlined by the blast that killed Chatah, although officials played down any link with the Saudi aid pledge.

Chatah, 62, a former finance minister and close aide to ex-premier Saad Hariri, a key Saudi ally, was killed along with seven other people in Friday's explosion in the heart of Beirut.

He was buried at the mausoleum of Hariri's father Rafiq, who was killed in a huge suicide bombing on the Beirut seafront in 2005 that supporters also blame on Hezbollah and its allies.

Hundreds of angry mourners chanted anti-Hezbollah slogans, as his coffin was brought into the mosque, draped in a green and cream-striped shroud inscribed with religious verses, alongside that of his bodyguard Tarek Badr.

Inside the mosque, the coffins were laid side by side, and one of Chatah's sons gripped a relative of Badr's, embracing him as they both wept.

'Martyr for moderation'

Outside, mourners in black watched the proceedings on a large screen, one waving a Lebanese flag.

Behind them stood a lit Christmas tree and a newly erected billboard declaring Chatah a "martyr for moderation".

Chatah was seen as an influential figure in the opposition March 14 coalition, which is opposed to the Syrian regime and Hezbollah, and many of its supporters said there was no doubt who had killed him.

Even though the multi-confessional army has legal responsibility for both domestic security and national defence, Hezbollah remains Lebanon's best-trained and equipped military force.

Hezbollah's huge arsenal has drawn persistent criticism from the March 14 opposition and its leader Saad Hariri, who accuse the militant group of abusing it to exert undue political influence.

Welcoming the Saudi aid pledge on Sunday, the opposition leader said it would help enable the Lebanon to exercise full state control.

The aid pledge marked an "exceptional step in the transition to a real state whose authority prevails over any other authority and whose army is not exceeded by any other army," Hariri said.

No one has claimed responsibility for killing Chatah, although the opposition has implied Damascus and Hezbollah were behind it.

"The criminal is the same, he who is thirsty for the blood of Syrians... he and his Lebanese allies," March 14 said.

Syria denied the "wrong and arbitrary accusations", while Hezbollah said the bombing was aimed at destroying "national unity".

Chatah is the ninth high-profile Syrian regime critic killed in Lebanon since Hariri's assassination, and his death comes as the war in Syria exacerbates tensions in ever-fragile Lebanon.

Hezbollah has dispatched fighters to help the Syrian regime battle rebel forces, while many Lebanese Sunnis support the Sunni-dominated Syrian uprising.

In recent months, bomb attacks have targeted Hezbollah's stronghold in south Beirut, as well as the mainly Sunni northern city of Tripoli, killing dozens of people.

On November 19, a twin suicide attack on the south Beirut embassy of Iran, which was claimed by the Al-Qaeda-affiliated Abdullah Azzam Brigades, killed 25 people.