The capital of Guinea-Bissau awoke to heavy bombardment Friday as artillery shells apparently fired by rebels landed in the city center, the Portuguese news agency Lusa said.

After the shelling, long bursts of heavy machine-gun fire were heard from the area where government forces are laying siege to rebel positions around a Bissau military garrison and the nearby international airport, the Portuguese ambassador to Guinea-Bissau said."It seems that government forces are advancing on the airport," Ambassador Francisco Henriques da Silva said on Portuguese radio RDP-Africa.

Guinea-Bissau, a former Portuguese colony on Africa's western tip, began a descent into civil war on June 7, when former military chief of staff, Brig. Anumane Mane, launched a mutiny at a garrison in Bissau, the country's capital.

Da Silva said the fighting in Bissau had subsided by midmorning and that only Red Cross and military vehicles were on the city's streets.

He also said all efforts at mediation had failed.

Gambian Foreign Minister Mohamed Sedat Jobe reportedly left the country Thursday after Mane's rebels snubbed his offer of talks. Talks proposed by religious and political leaders also failed.

Senegal's army has sent troops and artillery fire across the border, and troops from the Republic of Guinea, south of Guinea-Bissau, have also been fighting for the government.

In a clandestine broadcast, rebel spokesman Maj. Manuel De Santos Gomes said his forces would succeed in ousting President Joao Bernardo Vieira.