Heavy weapons fire heard in Guinea-Bissau capital BISSAU (Reuters) - - Heavy weapons fire echoed through the capital of Guinea-Bissau on Thursday, witnesses said, and soldiers surrounded the residence of former Prime Minister Carlos Gomes Junior, the frontrunner in a presidential election in the small West African state. The reason for the military action and Gomes Junior's whereabouts were not immediately known. Armed soldiers stopped journalists from approaching the residence, which is located almost opposite the Angolan embassy in the capital Bissau. Witnesses said the firing later subsided. Guinea-Bissau, an impoverished former Portuguese West African colony that has a history of coups and army revolts, is currently in the middle of two rounds of voting to elect a new president to replace Malam Bacai Sanha, who died in a Paris hospital in January after a long illness. There is some trouble. We don't know what it is. There is shooting, sporadic machine gun fire and there have been three loud bangs ... We hear it is coming from near Carlos Gomes Junior's house," a diplomat in the capital Bissau told Reuters. State television had stopped broadcasting. Gomes Junior, who fell just short of an outright majority in last month's first round of the presidential election, is meant to face Kumba Yala in the run-off on April 29, but Yala and four other candidates have said they will boycott the vote in protest over alleged first-round rigging. The shooting came just days after news that Angola, which is also a former Portuguese colony but because of its oil resources is much richer than Guinea-Bissau, was ending its military mission to help modernize the army in the smaller state. The Angolan mission, agreed in 2010, had been designed to help end the military coups that have plagued Guinea-Bissau since it won independence from Portugal in 1974. Reporting by Alberto Dabo in Bissau and David Lewis in bamako, Writing by Pascal Fletcher