Libreville - A bill to revise Gabon's constitution, which opponents say risks letting President Ali Bongo retain power indefinitely, cleared a hurdle after the country's lower house overwhelmingly approved it, sources said on Friday.State media made no mention of the development but two lawmakers present told AFP the bill was passed in a plenary session on Thursday and an official source who declined to give his name confirmed as much.The national assembly is composed almost entirely of members of the ruling Gabonese Democratic Party (PDG). The text now has to go before the senate prior to examination by the constitutional court.Opposition leader Jean Ping last month slammed proposed changes which he deemed liable to violate the principle of separation of powers and establish a "monarchy." Bongo has ruled the country of some two million since his father Omar Bongo, who took office in 1967, died in 2009 after 41 years in power.The new text places no limit on presidential terms, abolishes a minimum age for presidential candidates and provides for government ministers taking an "oath of allegiance" to the president.Violence broke out days after disputed presidential elections in August 2016. Tensions were further inflamed after Gabon's Constitutional Court upheld Bongo's victory despite Ping's claim of electoral fraud.The country faces legislative elections next year. Presidential spokesperson Ike Ngouoni Aila Oyouomi last month rejected Ping's criticism, insisting the bill comprises democratic "advances" such as holding a two-round presidential vote.