Soldiers have taken control of much of the capital of the Guinea-Bissau in what appears to be a coup attempt.Heavy gunfire was been heard in the city of Bissau and the residence of outgoing President Carlos Gomes was reportedly attacked.Troops have also taken control of the national radio station and the ruling party's headquarters.West African regional organisation Ecowas condemned what it described as an attempted coup.Mr Gomes came first in an inconclusive presidential election last month, but failed to win outright. His whereabouts and those of the interim President, Raimundo Pereira, are currently unknown, reports say.The second-placed candidate in the March election, former President Kumba Yala, has said he will boycott the run-off vote scheduled for 29 April.Mr Yala alleged that the election had been fraudulent.The emergency vote was called after the death in January of President Malam Bacai Sanha, after a long illness.Guinea-Bissau, an impoverished former Portuguese colony, has been plagued by a long series of coups since gaining independence in 1974.It has recently become an important staging post for gangs smuggling drugs from Latin America to Europe.