Lebanon needs more international help to fight jihadist forces that have launched a series of attacks against the army and kidnapped security forces, the country's prime minister told AFP.

Tammam Salam, speaking ahead of a visit to France this week, welcomed French arms deliveries due "in the coming weeks", but said his country's military needed more.

Lebanon's army, which has around 70,000 troops and is recruiting 10,000 more, "has showed respectable defence capacity", Salam said.

But "we need a lot more aid for it", he said.

Salam said Lebanon was not in danger of falling to jihadists from the Islamic State group or Al-Qaeda's Syrian affiliate, Al-Nusra Front.

He dismissed the possibility of "an Islamic caliphate in Lebanon" such as that declared by IS in parts of Syria and Iraq.

"The danger is that they will try to weaken Lebanon," he said.

Last December, Saudi Arabia pledged $3 billion to fund the purchase of French weapons to bolster Lebanon's military against jihadists.

Implementation of the deal has taken longer than expected, but Salam said the first arms deliveries were now expected within weeks.

"Things are moving -- I'm very confident," he said, speaking from his office at the Grand Serail residence in the capital Beirut.

"All the deals have been signed... We're in agreement on 90 percent of the types of weapons. The delivery should begin in the coming weeks."

Salam said the deliveries would include "helicopters and the weapons necessary to help the army properly defend against incursions and attack from abroad, particularly those by terrorists".

Lebanon has tried to insulate itself from the effects of the war in neighbouring Syria, but has been wracked by increasing instability and spillover from the nearly four-year conflict.

Salam said Britain was also helping to bolster Lebanon's defences, with a series of observation posts erected by British officers along part of the border with Syria.

He said the border posts went up several weeks ago in a restive part of eastern Lebanon where the army has battled jihadists coming from Syria.