LISBON (Reuters) - Heavy gunfire rang out briefly near Guinea Bissau‘s airport on Monday as government forces apparently tried to seize two army barracks held by rebels since Sunday, residents said. They said the gunfire in the district of Bra could be heard from about 0830 GMT and lasted about 15 minutes. The incident followed heavy fire overnight between rebels and government troops in the West African state. President Joao Bernardo Vieira accused former chief of staff Ansumane Mane of being behind the uprising, which he called a „desperate act“. Pledging to use all possible means to crush the revolt, Vieira said „defeat of the rebellion is only a question of time“. Mane, who was suspended from duty in January following charges that senior officers were involved in arms smuggling, was formally replaced over the weekend by another brigadier, Humberto Gomes. It was this reshuffle in the military hierarchy that appeared to have triggered the revolt, diplomats said.