A bomb attack targeting fans at a football match in Nigeria's restive northeast has killed at least 40 people, a police officer says.
"There has been a bomb explosion at a football field this evening and so far more than 40 people have been killed," said the officer who requested anonymity in the town of Mubi, which has seen previous attacks by Boko Haram Islamists.
The policeman's account was confirmed by a nurse at the Mubi General Hospital, who also requested anonymity, as the health worker was not authorised to discuss the attack with the media.
Mubi is located in Adamawa state, one of three in the northeast which has been under a state of emergency for more than a year as the military has tried to crush Boko Haram's five-year extremist uprising.
The area has been hit by far fewer Boko Haram attacks than other parts of the northeast, but the town was the site of a gruesome October 2012 massacre at a post-secondary technical college.
Scores of students were killed in their dorms, including many whose throats were slit.
The policeman said the bomb exploded at roughly 6.30pm local time at the pitch in Mubi's Kaban area and targeted fans who were trying to leave the field after watching a local club match.
It was not immediately clear if players were among the casualties, but the officer and the nurse said it appeared most of the victims were fans.
Boko Haram has carried out scores of attacks on targets it says are a product of Western influence, including sports venues and schools teaching a secular curriculum.
The group has killed thousands during its battle against the government since 2009, but the conflict has received unprecedented global attention over the last six weeks following the Islamists' mass kidnapping of more than 200 schoolgirls.
The girls were seized on April 14 from Chibok in Borno state, which shares a border with Adamawa.
