N'DJAMENA • Four female suicide bombers have attacked the Chadian island of Koulfoua on Lake Chad, killing at least 19 people and injuring 130 in an attack blamed by security sources on the militant Islamist group Boko Haram.

The swampy maze of islands in the border areas between Chad, Niger, Cameroon and Nigeria has become one of the main targets of Boko Haram fighters who can find easy cover in the waterways.

The militants are based mostly in Nigeria but have become a wider security threat to the region.

"The provisional death toll is 19 dead, including the four kamikazes, and 130 injured," state TV said on Saturday.

A United Nations official said there was an unspecified number of people displaced by Boko Haram-related violence on the island when the attackers struck.

Two of the blasts rang out from the centre of the market and a third in the street as people fled. All of the bombers were female, the security sources added.

Chad extended a state of emergency in the region last month after a double suicide attack that killed 12 people. But new restrictions, such as bans on motorised canoes aimed at stopping attacks, make it harder for aid agencies to reach the roughly 60,000 displaced people living there.

REUTERS, AGENCE FRANCE-PRESSE