More than 50 people were killed in a Boko Haram attack on an oil exploration team in northeast Nigeria earlier this week, military, medical and humanitarian sources have told AFP.

“The death toll keeps mounting,” said one source yesterday involved in dealing with the aftermath of Tuesday's attack near Magumeri, adding: “Now we have more than 50 and… more bodies are coming in.”

Details of the ambush, which was initially thought to be a kidnapping attempt, have been slow to emerge, as the military strictly controls access to Borno state, which has been the epicentre of Boko Haram violence.

Telecommunications and other infrastructure have been severely damaged or destroyed in the conflict, which has left at least 20,000 dead and more than 2.6 million homeless since 2009.

The military said on Wednesday that 10 people were killed in the attack, which targeted a team from the Nigerian National Petroleum Corporation (NNPC) and geologists from the University of Maiduguri.

But an aid agency worker in Magumeri, which is 50 kilometres (32 miles) northwest of the Borno state capital, Maiduguri, said: “As at 7:00 pm (1800 GMT) yesterday (Wednesday), 47 bodies were recovered from the bushes around Magumeri.

“Eleven of them were badly burned in the attack. They were burned alive in their vehicle, which was stuck in a trench.

“We buried them here because they couldn't be taken to Maiduguri.

“This evening (Thursday), six more bodies were recovered, including one soldier, and many more could be recovered because search and rescue teams are all over the place.”

A medical source at the Nigerian Army 7th Division headquarters at Maimalari barracks in Maiduguri said: “So far we have 18 dead soldiers. Ten were brought yesterday and eight more today.”

At the University of Maiduguri Teaching Hospital (UMTH), a medical worker said: “We have 19 bodies at the moment of civilians. Fifteen of them were vigilantes (civilian militia) and four were staff from the university.

“They have been taken for burial.”

The head of the academic staff union at the University of Maiduguri, Dani Mamman, confirmed they had received four bodies and said two of them were academics.

“We got the impression our staff on the team were rescued because that was what the military spokesman said yesterday,” he added.

“But we were shocked when we were given four dead bodies. This means it wasn't a rescue.

“We still have other staff that are yet to be accounted for.”