Cameroon's parliament has adopted a constitutional bill removing a two-term limit to allow President Paul Biya to extend his 25-year rule over central Africa's biggest economy past 2011.
Opposition lawmakers, who criticise the bill as a setback for democracy, stormed out of the chamber before the vote.
The proposed change was a major cause of riots in February that killed dozens of people, many shot dead by security forces.
The 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.
Analysts say the change, which coincides with 84-year-old Zimbabwe President Robert Mugabe's bid to extend his own 28-year rule, means Biya's 2011 re-election will likely be a formality.
Biya's Cameroon People's Democratic Movement (CPDM) enjoys a huge majority, controlling 153 of 180 parliamentary seats.
The 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.
Parliament members from the Social Democratic Front (SDF), the main opposition with 15 seats, walked out of the assembly in protest, saying parliament should not amend a constitution that emerged from cross-party negotiations in the early 1990s.
The bill, submitted just six days ago, was approved on Tuesday by the assembly's constitutional law committee which dismissed more than 20 opposition amendments. The plenary vote had originally been expected on Friday but was brought forward.
There was little visible reaction in the capital Yaounde, whose streets were empty late on Thursday due to heavy rain.
A Reuters reporter saw members of Cameroon's military rapid reaction force patrolling parts of the city on Wednesday night. The force has spent the last few months combating banditry near Cameroon's eastern border.
Biya won more than 75% of the vote in a 2004 election which opponents said was rigged. Biya's party denies cheating.