Maiduguri - Civilian vigilantes working with the military against Boko Haram on Friday said they had foiled a roadside bomb attack against worshippers at a mosque in a key northeast city.
The suspected remote-controlled device was planted by the side of the road in the Gamboru Market area of Maiduguri and was successfully defused by the police bomb squad.
As the bomb was being made safe, another device exploded nearby but there were no casualties as the area had been cordoned off, said civilian vigilante Babakura Adam.
"Our assumption is that the bombs were planted ahead of Friday prayers in the mosque just nearby," he told AFP in the Borno state capital.
"Of course, it's Boko Haram's handiwork because in the last few days several arrests have been made of suspected female suicide bombers."
On Tuesday, two female suicide bombers blew themselves up within minutes of each other at the busy Monday Market in Maiduguri, killing more than 45.
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Boko Haram, which was founded in the city more than a decade ago, was suspected as it has increasingly employed women as human bombs in recent months across northern Nigeria.
Adam said the arrests were made on Wednesday and Thursday.
On the discovery of the bombs on Friday, another member of the civilian joint taskforce, who have increased in number in Maiduguri in recent weeks, said the intention was to cause havoc.
"The bombs would have killed both traders and worshippers," said Musa Kalo, who was among the first on the scene after the vigilantes were alerted by a passer-by.
One witness, Kolomi Abba, described seeing wires from the device sticking out of the ground, while Kalo said the bomb was buried in dirt by the roadside.
The Gamboru Market is one of Maiduguri's biggest markets and would ordinarily have been packed with shoppers, traders and worshippers before and after Friday prayers.
The explosion of the second device, which happened at about 9:40 am (0840 GMT), destroyed markets and stalls. A large crater was seen at the scene, eyewitnesses said.
Fears have grown in Maiduguri about an upsurge in Boko Haram attacks, after the militants took over more than two dozen towns in Borno and two neighbouring states in recent months.