Soldiers arrested Guinea-Bissau's presidential front-runner Carlos Gomes Junior after staging an apparent coup in the chronically unstable west African country, his wife said on Friday.

Gomes, the outgoing prime minister tipped to win an April 29 run-off vote, was whisked away in a pick-up truck after troops assaulted their residence late on Thursday, Salome Gomes said when she returned to the house to collect some belongings.

Soldiers armed with rocket-launchers, rocket-propelled grenades and Kalashnikov rifles also took control of the ruling party headquarters and the national radio station and rounded up politicians, as gunfire resounded in the darkened streets of the capital Bissau on Thursday.