At least 15 people have been killed in a suicide bomb attack at a crowded market in Chad's capital, just days after Boko Haram claimed a previous bombing in the city that left 38 people dead.
Saturday's attack in N'Djamena by a man disguised as a woman in a full-face veil came after a botched bombing in the capital of Nigeria's Borno state, Maiduguri, which killed two pedestrians.
Militant fighters on Friday night also raided the village of Ngamdu, some 100 kilometres from Maiduguri, killing 11, a member of the civilian militia said.
Both attacks again underlined the threat still posed by the Islamists, despite claimed military successes in recent months and with a new regional force set to deploy at the end of the month.
Experts said the bombing in Chad, following previous strikes in Niger and repeated targeting of northern Cameroon, showed the need for a joined-up solution involving Nigeria and its neighbours.
Nigeria's President Muhammadu Buhari, who came to power on May 29, has made defeating Boko Haram a top priority.
But Ryan Cummings, chief Africa analyst with the Red24 consulting group, told AFP: "The fight against Boko Haram is unlikely to be concluded with any rapidity.
"The fact remains that while Boko Haram continues to be defined as a Nigerian problem, evidence suggests that it has become a quandary of regional proportions requiring a regional solution.
Police director-general Taher Erda said the bomber detonated his explosives belt when he was stopped at the entrance to the market for security checks.
The provisional toll was 15 dead and 80 injured, four of them seriously, said police spokesman Paul Manga. Nine of the victims were female traders and one was a police officer, he added.
An AFP correspondent there described a gruesome scene of carnage and pools of blood.
The area, in the heart of the capital, was cordoned off by security forces after the attack at about 8:45 am (0745 GMT), and a police source said there was "no doubt it was Boko Haram".
Prime Minister Kalzeube Pahimi Deubet called a crisis meeting to discuss the attack.