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 immediately 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 religious extremism. Boko Haram also has attacked Christians outside churches and teachers and schoolchildren, as well as government and military targets. 

Since 2010, the militants have been blamed for the killings of more than 1,700 people, according to a count by The Associated Press.

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 gloats over recent attacks, threatens more, and even says his group is now strong enough to go after the United States.

The mosque slayings occurred Sunday morning in Konduga town, 35 kilometers (22 miles) outside Maiduguri, the capital of Nigeria's Borno state. 

A state security service agent and Usman Musa, a member of a civilian militia that works with the military, said Monday they counted the bodies at the mosque after the attack. Musa said four members of his group _ known as the Civilian Joint Task Force _also were killed when they reached Konduga and encountered “fierce resistance from heavily armed terrorists.”

Musa and the security service agent said the attackers wore military camouflage 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, 5 kilometers (3 miles) outside Maiduguri, where Musa said he counted 12 bodies of civilians.

Twenty-six worshippers at the mosque were hospitalized with gunshot wounds, said a security guard at the emergency ward of Maiduguri Teaching Hospital. He and the state security agent both spoke on condition of anonymity because they were not allowed to give information to reporters.

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 northeastern towns and villages in this nation of more than 160 million people, which is divided almost equally between the predominantly Muslim north and the mainly Christian south.

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

“You soldiers have claimed that you are powerful, that we have been defeated, that we are mad people,” Shekau says, speaking in the local Hausa language. “But how can a mad man successfully coordinate recent attacks in Gamboru, in Malam Fatori, slaughter people in Biu, kill in Gwoza and in Bama, where soldiers fled under our heavy fire power?

“We have killed countless soldiers and we are going to kill more.”

He further insists the extremists' “strength and firepower has surpassed that of Nigeria. ... We can now comfortably confront the United States of America.”

Shekau also said Nigeria's military is “lying to the world” about its casualties. “They lied that they have killed our members, but we are the ones that have killed the soldiers.”

He apparently was referring to Aug. 4 attacks on a military base at Malam Fatori and a police outpost in Bama, both near the border with Cameroon. Joint Task Force spokesman Lt. Col. Sagir Musa told reporters 32 extremists, two soldiers and one police officer were killed. But when the Borno state governor called on the head of the task force to commiserate, Maj. Gen. Jah Ewansiah told him in front of reporters that they lost 12 soldiers and seven policemen. Nigeria's military regularly lowballs casualty figures of civilians and military.

Under orders from the military, cellphone and Internet service has been cut in Borno, making communications difficult. The military says the extremists were using cellphones to coordinate attacks. But some government officials argue that the lack of communication prevents civilians from informing them of suspicious movements and getting help when they are attacked. (AP)