Former Lebanese prime minister Saad Hariri, exiled in France since 2011, said Monday he would return to his country for November legislative elections, adding that he hoped to become premier again.

Lebanon is in the throes of political turmoil since the March 2013 resignation of prime minister Najib Mikati.

President Michel Sleiman's mandate runs out on May 25. and there are fears that a successor will be hard to find because of huge disagreements between Lebanon's pro- and anti-Syria blocs.

"I will return to Lebanon for the elections and will one day become prime minister," Hariri, who served as prime minister between 2009 and 2011, told France's Europe 1 radio.

Legislative elections have been pushed back to November but it is not clear whether a presidential election, due in May, will be held on schedule.

Tensions have soared in Lebanon since the outbreak of the war in neighbouring Syria, as the Lebanese Shiite Hezbollah movement has sent troops to back the regime of President Bashar al-Assad while their rivals in a Western-backed coalition have supported the Sunni-led rebels.

Saad Hariri heads the pro-Western and anti-Syrian March 14 coalition, formed after the assassination of his father Rafiq Hariri, who was killed in a massive car bombing in Beirut in February 2005.

Four Hezbollah members are being tried in absentia at a special UN tribunal at The Hague over the blast that killed the billionaire former prime minister.

"For 50 years, political assassinations were part of Lebanese politics," Saad Hariri said. "For the first time a court is trying to put an end to impunity."

"The accused are Hezbollah members. The Hezbollah has a hierarchy. Everybody knows it was Bashar al-Assad who gave the order," he said.

The Special Tribunal for Lebanon (STL) is unique in international justice as it was set up to try the perpetrators of a terrorist attack and because it can try the suspects in absentia.

Rafiq Hariri, Lebanon's Sunni prime minister until his resignation in October 2004, was on his way home for lunch when a suicide bomber detonated a van full of explosives equivalent to 2.5 tonnes of TNT as his armoured convoy passed.

The February 14, 2005, blast killed 22 people as well as Hariri, and wounded 226.