UPDATE 1-Cameroon's Biya signs law allowing third term bid

(Adds details, background)

YAOUNDE, April 15 (Reuters) - Cameroon President Paul Biya on Tuesday signed into law a constitutional change which removes a two-term limit, allowing him to extend his 25-year rule over central Africa’s biggest economy, state radio said.

The country’s parliament, where Biya’s Cameroon People’s Democratic Movement (CPDM) dominates with a majority of 153 of the 180 seats, had approved the constitutional amendment last Thursday, opening the way for its promulgation.

Opposition leaders have sharply criticised the change, which will allow Biya to be re-elected in 2011, as a setback for democracy and a “hold-up” by the president, who took power in 1982 and is one of Africa’s longest serving leaders.

The amendment was a major cause of riots in February that killed dozens of people. Cameroon’s security forces have been patrolling the capital Yaounde and other cities in recent days to prevent any unrest.

February’s violence shook the world’s fourth biggest cocoa grower, which ranks in sub-Saharan Africa’s top 10 economies.

Cameroon lies on the oil-rich Gulf of Guinea, though its modest crude oil output of around 90,000 barrels per day is half its 1980s peak.

The ruling CPDM oversaw the introduction of a new constitution in 1996 which limited presidents to two seven-year terms. Biya’s second term under that constitution expires in 2011, but he made it clear in a New Year speech that he would like to stay on.

When the constitutional amendment was passed by parliament on Thursday, deputies from the Social Democratic Front (SDF), the main opposition with 15 seats, walked out of the assembly in protest. They said parliament should not amend a constitution that emerged from cross-party negotiations in the early 1990s.

Biya won more than 75 percent of the vote in a 2004 election which opponents said was rigged. Biya’s party denies cheating.

A number of African presidents have abolished two-term limits introduced in the 1990s in a wave of multi-party rule after the end of the Cold War. But efforts to do so in Nigeria, Zambia and Malawi have been blocked in recent years. (For full Reuters Africa coverage and to have your say on the top issues, visit: (Editing by Pascal Fletcher and Mary Gabriel)