At least 27 people were killed and 90 injured in a series of blasts on Saturday, Chadian officials said.

"Three suicide bombers blew themselves up in three different places at the weekly market on [...] an island in Lake Chad," a security source from the Chadian capital N'Djamena told the AFP news agency.

All three of the suicide bombers were female, according to the police.

The authorities suspect the Islamist group Boko Haram is behind the attack, said Chad gendarmerie director general Banyaman Cossingar.

The Islamic insurgents wage most of their fighting in Nigeria, although they have also conducted terror strikes in Chad, Niger and Cameroon.

Boko Haram under strain

Four weeks ago Chadian authorities declared a state of emergency in the region following a wave of Boko Haram attacks.

More than 5,000 soldiers have been deployed to islands and lakeside villages in the Lake Chad area. Chad shares the lake with Nigeria, Niger and Cameroon.

Chadian troops also play a key role in the regional alliance against Boko Haram, with the coalition troops reclaiming large swathes of territory from the group during recent months.

In response, the militants have boosted terror strikes against civilians.

Thousands of people fled to the island of Koulfoua earlier this year to avoid the violence.

dj/jlw (AFP, Reuters, dpa)