(Adds bid to stop return of illegal immigrants, paragraph 7)

By Ahmed Ali Amir

MORONI, April 2 (Reuters) - Comoros' Anjouan island expects to organise democratic elections within three months, its interim leader said on Wednesday, a week after his predecessor was ousted in an African Union-backed offensive.

Former president of Anjouan's appeals court, Lailizamane Abdou Cheik, was sworn in as the tiny, wooded island's interim leader on Monday to replace Mohamed Bacar.

Bacar, a French-trained former gendarme, seized power in 2001 and clung on after an illegal election last year before being toppled by troops from the Comoros and the AU.

"Our main mission is to manage to organise presidential elections on the island in a manner that is free and transparent," Cheik said by telephone.

"We have a deadline of three months," he added.

With its history of assassinations, mercenary invasions and 20 or so coups and attempted rebellions since independence from France in 1975, Comoros is still struggling to establish political stability.

Bacar escaped to the nearby French-run island of Mayotte and Comoros has reacted angrily to France's refusal to extradite him, while repatriating other illegal immigrants from Comoros.

"If France refuses to extradite Mohamed Bacar, wanted by Comoros' justice system, then why expel the others?" government spokesman Abdourahim Said Bacar asked.

The Comorian government questions why Bacar would be treated differently, especially since there is an outstanding arrest warrant against him.

In response the government sought to stop the return of any of its citizens from Mayotte.

"It is strictly forbidden for all travel agencies, air or sea, national or foreign, to transport Comorian illegal immigrants from Mayotte until further notice," an official note sent to air and shipping companies in Comoros on Wednesday said.

Suspicions of the former colonial power have been compounded by the crash-landing of a French government helicopter that had been flying in Comorian airspace without permission, days before the Anjouan assault.

Comoros, the spice and perfume-producing Indian Ocean archipelago is one of the world's most indebted nations, with most of its 700,000 people living on less than $1 a day.

In recent months, however, Comoros has received investment pledges worth tens of millions of dollars from investors in Kuwait and Dubai.

Lying off Africa's east coast, the islands -- which grow ylang-ylang, vanilla and cloves -- were first settled by Arab seafarers 1,000 years ago, then later became a pirate haven. (Additional reporting Ed Harris in Port Louis, Editing by Bryson Hull and Matthew Jones) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

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