Kano: Four people killed were killed on Monday when a suicide bomber hit a military checkpoint on the outskirts of the northeastern Nigerian city of Maiduguri, civilian vigilantes told AFP.
The blast happened at about 12:10 pm (1110 GMT) at the Jimtilo checkpoint, as passengers arriving in Maiduguri were being screened, they said.
"The bomber killed four people and injured five others," said Babakura Kolo, who is part of the militia assisting the military against the insurgents.
"The dead included two civilian JTF (joint task force or vigilantes) and a policeman. Two immigration officers are among those injured."
Vigilante Umar Bulunkutu gave the same toll.
On Saturday, two people were killed in Maiduguri when two suicide bombers in a motorised rickshaw tried to target a busy bus station but were foiled by heavy security.
Just over an hour later, a man disguised as a woman and wearing a full-face veil blew himself up at a crowded market in Chad`s capital, N`Djamena, killing 15 people.
The attacks come as Nigeria and its neighbours gear up to deploy a strengthened regional force against Boko Haram, which has increased the frequency and intensity of its attacks on civilians.
Maiduguri, where the group was founded in 2002, has been repeatedly targeted and since Muhammadu Buhari became president on May 29, nearly 570 people have been killed in Nigeria alone.
Danlami Ajaokuta, another civilian vigilante, said the bomber struck in the middle of the crowd of passengers.
"It is standard procedure at the checkpoint for passengers to alight from their vehicles and walk some distance to a shed manned by the soldiers," he explained.
"They identify themselves before they trek some more distance past the checkpoint and then enter their vehicles and move on."
Residents in Maiduguri have been on edge for months over the wave of new attacks and one, Ibrahim Buba, said the explosion rocked the city.
"We later saw two military jets flying southwards," said Ibrahim Buba, who lives nearby.
"One of them later returned and we learnt that the jets were in pursuit of some Boko Haram gunmen that were sighted in the bush, apparently planning to attack the city."
Buhari, who has vowed to crush the militants, is coming under pressure because of the mounting death toll and the military`s apparent inability to stop attacks on civilian "soft" targets.
On Monday he sacked the military top brass he inherited from his predecessor Goodluck Jonathan.
Before he was removed as chief of army staff, Lieutenant General Kenneth Minimah told a conference in Abuja that troops had "achieved tremendous success" in recent months.
"Today, their (Boko Haram`s) ability to face our gallant troops in any form of combat has been seriously degraded," he said.
"Consequently, the terrorists have cowardly resorted to attacking innocent and vulnerable citizens in markets, places of worship and similar places."