President Mohamed Taki, whose government had lost control of two of the Comoros federation's three islands, ignored appeals from France and the Organisation of African Unity on yesterday and sent in about 300 troops to restore central authority on Anjouan, which announced its secession last month.
Witnesses said the government forces had pressed into service the rubber dinghies normally used by gendarmes patrolling to protect the islands' sea turtles - a major tourist attraction.
Troops met resistance outside Mutsamudu, the main town on Anjouan, and had not yet entered the town late yesterday. They were expected to do so today, witnesses said.
Residents reported fighting around the airstrip at Ouani and at the town of Domoni.
An Aero Marine flight from Moroni taking food and other supplies to Comoran troops failed to land in Ouani and returned with its cargo.
Comoran officers had arrested 15 Red Crescent volunteers who tried to help those hurt in yesterday's violence, officials said.
"Mutsamudu is a small town with narrow streets and very little else. I don't know what it will look like if heavy weapons are used there." an Anjouan resident said by radio.
Mr Taki's government gave no indication of casualty figures. Telephone links with Anjouan were cut but islanders in sporadic touch with the outside world by radio reported clashes near Mutsamudu.
After days of sabre-rattling and preparations, two boatloads of soldiers landed in Anjouan early in the morning, according to the French foreign ministry in Paris and diplomats in Moroni, capital of the Indian Ocean archipelago.
"The security forces are progressively re-establishing the republican order, the freedoms and the safety of persons in Anjouan, mainly in Mutsamudu and Domoni," a statement from Mr Taki's presidency said.
Radio Comoros called the secessionists in Anjouan "drunkards and drug addicts".
Residents said the soldiers landed in rubber dinghies at Ouani, four miles east of Mutsamudu. The commandeered ships which ferried them from Moroni and anchored out of range of defenders' weapons.
Anjouan, the second largest of the three-island group, seceded on 3 August after months of protest, civil unrest and clashes with security forces that led to several deaths.
The smallest of the picture-postcard islands, Moheli, followed suit, leaving Mr Taki's government in control of only Grande Comore.
Political leaders on the two secessionist islands have disagreed on whether they want full independence, a return to French rule or merely greater autonomy.
But all agree that the federation formed at independence from France in 1965 has meant only poverty for most of the country's 671,000 people and a succession of coups for their politics.Reuse content