YAOUNDE - Cameroon's president replaced the heads of the national police force and the intelligence service in a security shakeup that follows local media reports of a coup plot.

Political tension has been rising in the central African oil producer ahead of 2011 elections in which long-serving President Paul Biya is expected to seek another term in office.

Former police chief Emmanual Edou has been replaced by Martin Mbarga Nguele, and DGRE intelligence unit head Jean Marie Obelabout has been replaced by Maxine Leopold Eko Eko, according to state radio.

No reason was given for the changes but local media reported they may be linked to widespread rumours of a foiled coup plot on July 17 when Biya was in France.

The government also named Paul Nji Atanga, former minister in charge of missions at the presidency, as the first permanent secretary of the National Security Council (NSC), a body created in 2009.

Biya, in power since 1982 and one of Africa's longest serving presidents, has not said he will stand in the 2011 elections, but he changed the constitution in 2008 to relax presidential term limits and is widely expected to run.