Suspected Boko Haram militants have killed at least 74 people in two north-eastern Nigerian villages in separate attacks, the police said.

Riding in all-terrain vehicles, the Islamic extremists arrived in Kawuri village, shot down people at a marketplace and set off bombs around the village . They also killed people in their homes and many died in a fire when their dwellings were set ablaze.

"No house was left standing," Ari Kolomi, who fled the village in Borno, told AP.

"The gunmen were more than 50 [in number]; they were using explosives and heavy-sounding guns," he said. Kolomi did not know if his relatives had survived the attack.

Isa Ibrahim, another witness, told CNN that the attackers initially pretended to be traders at the market and they used bombs which were probably planted ahead of the raid.

The same day, armed militants opened fire on a busy Catholic church service in Waga Chakawa village in the state of Adamawa, an army spokesman said. They are also reported to have set off bombs, burning houses and taking residents hostage during the coordinated attack on the village which lasted four hours, according to Reuters.

Father Raymond Danbouye, spokesman for the Catholic Diocese of Yola, said at least 22 people were killed in the church siege.

Boko Haram, which means "western education is forbidden", is an Islamic extremist organisation which is being blamed for both the attacks.

Christian minorities, security forces and resisting politicians have been the group's traditional targets in the Muslim north.

The militants have apparently waged a sustained campaign in northern Nigeria to impose Sharia law, and to turn the region into a conservative Islamic state.

Borno and Adamawa are two north-eastern states where President Goodluck Jonathan had declared an emergency last year in a bid to launch a dedicated offensive against Boko Haram.

The state's long battle against the militia in NE Nigeria has largely been unsuccessful and the affected regions continue to be marred by violence.

Earlier, this month President Goodluck sacked his military high command, without formally stating any reason. But experts say the decision may have been influenced by the failure of the army to rein in the insurgency.