MAIDUGURI, Nigeria — Suspected Islamic militants wearing army fatigues gunned down 44 people praying at a mosque in northeast Nigeria, while another 12 civilians died in an apparently simultaneous attack, security agents said Monday.

Sunday’s attacks were the latest in a slew of violence blamed on religious extremists in this West African oil producer, where the radical Boko Haram group, which wants to oust the government and impose Islamic law, poses the greatest security threat in years.

It was not clear why the Islamic Boko Haram would have killed worshipping Muslims, but the group has in the past attacked mosques whose clerics have spoken out against extremism. Boko Haram also has attacked Christians, teachers and children, as well as government and military targets.

Since 2010, the militants have been blamed for the killings of more than 1,700 people.

The news about Sunday’s violence in Borno state, one of three in the northeast under a military state of emergency, came as journalists received a video featuring Boko Haram leader Abubakar Shekau, who threatens more violence and even says his group is strong enough to go after the United States.

The mosque slayings occurred Sunday morning in Konduga.

A state security service agent and Usman Musa, a member of a civilian militia that works with the military, said the attackers wore uniforms used by the Nigerian army, which they may have acquired in one of their attacks on military bases.

On their way back from Konduga, the security forces came upon the scene of another attack at Ngom village near Maiduguri, where Musa said he counted 12 bodies of civilians.

Twenty-six worshippers at the mosque were hospitalized, said a security guard.

Nigeria declared a state of emergency in much of the northeast on May 14 to fight the onslaught after Boko Haram fighters took over several towns in this nation of more than 160 million people, which is divided between the Muslim north and the Christian south.

In the video, Shekau brushes off any gains asserted by the security forces.

“We have killed countless soldiers and we are going to kill more,” he said, further insisting “We can now comfortably confront the United States of America.”