ANJOUAN, Comoros - The Comoros government captured the capital of the rebel-held island of Anjouan on Tuesday, just hours after an African Union-backed military operation got under way to oust a renegade colonel who took power in May, a defense official said.

Explosions and gunfire started ringing out before dawn as hundreds of troops moved in as part of a long-threatened invasion. There was no immediate word on casualties.

"We have now taken the Anjouan capital," Defense Chief of Staff Mohamed Dosara said by telephone from the main island of Grand Comore. "We have met a small amount of resistance."

Anjouan island's seaport was under the control of AU troops, according to an Associated Press reporter at the scene.

However, about a dozen armed men, who identified themselves as loyalists to renegade Col. Mohamed Bacar, appeared in control just over a mile outside the capital, Mutsamudu, and awaiting an attack.

The Comoros, an archipelago of three main islands 250 miles off Africa's southeast coast with a population of about 750,000, has been caught up in a series of coups and political upheavals since gaining independence from France in 1975. The late Bob Denard, a notorious French mercenary, controlled the Comoros behind a figurehead leader for most of the 1980s following a coup he led.

Bacar's takeover of Anjouan island drew increasingly strident warnings from the central government.

Dosara said troops were searching for Bacar, a former president of Anjouan who has said he is seeking the island's independence.

Mohamed Kassim Adong, a resident of the coastal Anjouan town of Domoni, said he saw soldiers going house-to-house conducting searches.

Several hundred soldiers, including at least 80 AU troops from Tanzania, were among the initial landing force that arrived aboard four ships, authorities said. About 100 Comoros military reinforcements later arrived by sea, along with six pickup trucks mounted with machine guns, and began fanning out on the island.

One Comoros officer, who asked that his name not be used because he was not authorized to speak publicly, said government forces had arrested three "high-ranking officers" loyal to Bacar.

Officials at African Union headquarters in the Ethiopian capital, Addis Ababa, refused to comment.

The morning's explosions and gunfire drew hundreds of people into the streets of Anjouan, some of them chanting "Bacar is a dog" and "We have won!"

On Monday, the country's president said the army would invade Anjouan and helicopters dropped leaflets over the island urging residents to avoid the pending fighting.

"The National Army of Development (AND) informs all the residents that it will be in Anjouan in the days, or rather the hours coming," the leaflets read. "It is therefore advised that residents do not stray too far from their residences."

Each of the three main islands of Comoros has a regional president under the country's main leader, President Ahmed Abdallah Sambi, who is based in Moroni on Grand Comore.

"I have ordered the army to invade Anjouan to liberate the island from the hands of Mohamed Bacar," Sambi said in a news conference.