Lebanon on Saturday announced the formation of a compromise government after a 10-month political vacuum during which the war in neighbouring Syria exacerbated longstanding divisions.

The 24-member government unites the powerful Shiite movement Hezbollah and its allies with the Sunni-led bloc of former prime minister Saad Hariri for the first time in three years.

"After 10 months of efforts, of patience, a government protecting the national interest is born," said Tammam Salam, Lebanon's new prime minister.

"It is a unifying government and the best formula to allow Lebanon to confront challenges," said Salam, who was tasked with forming the government back in April 2013 after the resignation of his predecessor Najib Mikati.

The announcement ends a political stalemate that left Lebanon without a government even as the conflict next door spilled over, with car and suicide bomb attacks striking Beirut and elsewhere.

Multiple attempts to resolve the government crisis stumbled over disagreements between the Hezbollah and Hariri blocs, which back opposing sides in the Syrian conflict.

Hezbollah is allied with Syria's President Bashar al-Assad and has dispatched fighters to bolster his regime in its fight against an uprising.

Hariri is a fierce opponent of the government in Damascus and backs the Sunni-led uprising against Assad.

Saturday's compromise, which has been months in the making, is intended to ensure neither the Hezbollah nor the Hariri bloc has veto power over the other.

It divides the 24 portfolios into three groups, with Hezbollah and Hariri's blocs each taking eight ministries, and the final eight going to candidates considered to be neutral.

To preserve the delicate balance between the country's 18 sects, the government is also equally divided between Christian and Muslim representatives.

Hariri paved the way for the breakthrough when he announced in a U-turn last month that he was willing to allow his so-called March 14 bloc to join a government with Hezbollah.

Bitter pill

The decision was a bitter pill for the former prime minister, who is fiercely opposed to Hezbollah.

Five members of the group are currently on trial in absentia at a special court in The Hague for their alleged involvement in the 2005 assassination of his father, former prime minister Rafiq Hariri.

Hariri's decision has not been welcomed by all those in his bloc, with the Christian party Lebanese Forces refusing to join any government that includes Hezbollah.

Sources within March 14 said Hariri had made a number of "concessions" to Hezbollah, which won several key portfolios for its Christian ally Michel Aoun.

His son-in-law Gebran Bassil becomes foreign minister, and fellow bloc member Arthur Nazarian will be charged with the powerful energy ministry.

Hariri also reportedly compromised on two initial candidates for interior minister, both of which were rejected by Hezbollah's bloc, party sources said.

Hariri has said his decision was justified by the country's desperate need for leadership as it struggles with the spillover from the war in Syria.

In recent months, a string of bomb attacks have rocked the capital Beirut and other parts of the country.

The attacks have largely targeted areas considered Hezbollah strongholds, though the victims have been civilians, and have been claimed by jihadist groups in response to the movement's role in Syria's war.