Saudi Arabia has pledged $3 billion for the Lebanese army to buy equipment from France, Lebanese President Michel Sleiman announced on Sunday.

The kingdom "decided to provide generous assistance to Lebanon in the form of $3 billion for the Lebanese army to strengthen its capabilities," Sleiman said, 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 answering a question about Sleiman's announcement that came as the French leader arrived in Riyadh for talks with King Abdullah.

The aid pledge comes amid mounting sectarian tension in Lebanon related to the war in neighbouring Syria.

Lebanon's powerful Shiite Hezbollah movement is fighting alongside President Bashar al-Assad's forces against an uprising that many Lebanese Sunnis support.

Saudi Arabia is a leading backer of the rebels battling Assad's regime, which has relied on strong support from Shiite Iran.

Sleiman's announcement comes two days after a bombing that targeted a leading critic of Hezbollah and the Syrian regime, though the Saudi aid pledge did not appear to be directly related.

He said the money would be used to buy weapons from France, pointing to the "historical ties that link it to Lebanon and the depth of the military cooperation between the two countries".

Sleiman did not specify what weapons would be purchased.

Lebanon's armed forces are woefully under-equipped and face multiplying security challenges, underlined by the bomb attack on Friday and rockets fired from Lebanon into Israel on Sunday that prompted return fire from the Jewish state.

The armed forces are responsible for domestic security as well as national defence, and contain members from across Lebanon's multi-sectarian population.

The powerful Hezbollah movement remains the country's best-armed and trained organisation however, and its arsenal has drawn domestic criticism, including from former prime minister Saad Hariri and the so-called March 14 coalition.

Hariri, whose father was assassinated in an attack blamed on Hezbollah, welcomed the Saudi pledge and said it came as part of a project to impose state control.

Sleiman "announced 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 in a statement.

Sleiman visited Saudi Arabia last month.