MAIDUGURI/YOLA, Nigeria, June 1 (Reuters) - A bomb blast targeting a television viewing centre for football in northeast Nigeria killed an unknown number of people on Sunday, a police spokesman said.
A military source said several bodies had been recovered from the site of the evening bombing in the town of Mubi in Adamawa state.
"We don't have a precise death toll for you while work is still going on to remove the corpses," said police spokesman for Adamawa state Usman Abubakar.
There was no immediate claim of responsibility. Islamist militant group Boko Haram, whose struggle for an Islamic state is concentrated in the northeast, would be the prime suspect.
The group has set off several bombs across north and central Nigeria in the past two months.
Last weekend, a suicide bomber set out to strike an open-air viewing of a football match in the central city of Jos, but his car blew up before reaching the target, killing three people.
A suicide bombing the week before in Jos killed 118 people, and two bombs on the outskirts of Abuja in April killed 95 between them.
The group is still holding more than 200 schoolgirls that it abducted on April 14.
Nigeria's president said on Thursday he had ordered "a full-scale operation" against Boko Haram and sought to reassure parents of the kidnapped girls that their children would be freed.
Since the girls were taken, Boko Haram fighters have killed at least 500 civilians, according to a Reuters count.
Two Italian priests and a Canadian nun, kidnapped in northern Cameroon nearly two months ago by suspected Boko Haram gunmen, were released on Sunday, smiling and apparently in good health as they arrived in the capital.
Cameroonian security forces killed some 40 Boko Haram militants in clashes in the country's far north, state radio said on Sunday. A presidency source confirmed the clashes, which took place west of the town of Kousseri, in the region bordering Nigeria and Chad.
Nigeria has accused Cameroon of not being tough enough on the militants hiding in its border region.
(Reporting by Lanre Ola and Imma Ande; Writing by Tim Cocks; Editing by Cynthia Osterman and Mohammad Zargham)