Boko Haram insurgents attacked a market outside the key northeast Nigerian city of Maiduguri, local people who witnessed the incident told Agence France-Presse on Saturday.

About 50 gunmen on motorbikes stormed the weekly market in Ngom village, some 20 kilometers (12.5 miles) from the Borno state capital, at about 1:00 pm (1200 GMT) on Friday and opened fire, they said.

Nigeria's military on Friday claimed to have routed Boko Haram militants near the Borno state capital Maiduguri, as residents in another under-siege town complained of food shortages and hardship.

Army spokesman Timothy Antigha said in a statement that the Islamists launched a "massive" attack on the town of Konduga, about 35 kilometers (22 miles) from Maiduguri, at 0430 GMT Friday.

Boko Haram fighters have surrounded the northeast Nigerian city of Maiduguri and are preparing an imminent takeover, an influential regional group claimed on Thursday, calling for military reinforcements.

"They have completely surrounded the city of Maiduguri," said the Borno Elders Forum, which is made up of retired senior civilian and military officials as well as community leaders.

Nigeria's military launched ground and air offensives against Boko Haram to recapture the northeastern town of Michika that fell to the jihadist militants over the weekend, witnesses said on Wednesday. 

Hundreds of troops aided by military jets have been pounding Boko Haram positions in Michika in Adamawa state since Sunday, residents of nearby towns and villages told Agence France Presse.

Twenty Nigerian police officers are still missing three weeks after Boko Haram fighters attacked a training academy outside the remote northeastern town of Gwoza, the country's police chief said on Tuesday. 

A U.S. air marshal was attacked with a syringe at the airport in Lagos, Nigeria and had been hospitalized, the FBI said Monday.

Cameroon said on Monday its soldiers had killed "more than 100" Boko Haram fighters during an attempted incursion by the Nigeria-based Islamist insurgents, while across the border thousands continued to flee the group's advances.

Christians in northeast Nigeria are paying a heavy price at the hands of Boko Haram, even if they are not being targeted specifically by the militants in their bloody quest for an Islamic state.

Thousands of fear-stricken residents in several towns and villages in Nigeria's northeast Adamawa state have fled their homes after troops failed to retake a major town seized by Boko Haram militants, residents said Saturday.

When Nigeria's new chief of defense staff was appointed earlier this year, he promised a swift end to the deadly violence being waged by Boko Haram Islamists.

"If we do our work cohesively, I can tell you we will finish that thing (the counter-insurgency) in no time," Air Marshal Alex Badeh said at his investiture on January 20.