A gunbattle in Guinea-Bissau has killed at least six people, as the troubled West African state tries to recover from a military coup that derailed a presidential election earlier this year.

Sources told Western news agencies that the fighting began when unidentified gunmen attacked a military base near the capital, Bissau, before dawn Sunday, prompting soldiers to return fire and repel the assault. They said most of the dead appeared to be assailants. Casualties among the security forces could not be immediately confirmed.

A military junta seized power in Guinea-Bissau in April, interrupting a presidential election between the first and second rounds. The coup leaders installed a transitional government in May to organize new elections, winning the support of West African regional bloc ECOWAS.

Guinea-Bissau has suffered chronic unrest since independence from Portugal in 1974, with frequent coups and counter-coups. The instability has made the country a hub for international cocaine traffickers.