"His passport has been given back to him and he's bought a ticket. He will land in Bahrain at 3 p.m. (1100 GMT)," Abbas al-Amran, a friend of Hassan Mushaimaa told Reuters.
Hardline Shi'ite opposition leader Hassan Mushaimaa, London-based leader of the Shi'ite Haq movement, said on his Facebook page on Monday he would try to return to the Gulf Arab country after a week of unprecedented protests by majority Shi'ite Muslims against the U.S.-backed Sunni monarchy.
He said he wanted to see if the island nation's leadership was serious about dialogue or not.
But he was stopped during a stopover in Beirut by Lebanese authorities, who said his name was on an international arrest warrant, and his passport was seized.
On Thursday Bahrain's foreign minister said Mushaimaa, who was among 25 people charged over an alleged coup plot and who was being tried in absentia, had been pardoned and would be allowed to return home to join a national dialogue.
Security forces killed seven people and wounded hundreds while trying to disperse protests last week before Bahrain, under pressure from its Western allies, pulled back its army and police and allowed peaceful demonstrations in Pearl Square.
Bahrain's protesters want a constitutional monarchy instead of the existing system where citizens vote for a mostly toothless parliament and policy remains the preserve of a ruling elite centred on the Sunni al-Khalifa dynasty.
Mushaimaa's Haq party is more radical than the Shi'ite Wefaq party, from which it split in 2006 when Wefaq contested a parliamentary election. Haq's leaders often have been arrested in recent years, only to receive royal pardons.