Dozens of people have been killed in another suspected rampage by Islamist militant group Boko Haram in northern Nigeria.

The group is believed to be behind a string of attacks in the Madagali and Michika Local Government Areas, in Adamawa State, on Wednesday.

Gunmen armed with rocket propelled grenades and explosives descended on Kirchiga Village before turning their weapons on Shuwari, Shuwa and Michika Town.

At least 28 people were killed and an unknown number injured.

The Nigerian station Channels TV reported that three Catholic churches were set ablaze in Michika Town and that three Catholic nuns may be among the victims.

In Shuwa Village, Saint Joseph's Minor Seminary was set on fire, as well as the home of a former commissioner and a maternity health centre.

The attackers also torched homes and looted shops and other property.

In another attack on Wednesday, unknown gunmen killed two members of the same family in Diyam-Rim village, in the Riyom Local Government Council of Plateau State.

The attacks have been condemned by Christian Solidarity Worldwide's Mervyn Thomas, who warned that a "brutal and indiscriminate onslaught" was taking place in the region.

"The continuing loss of innocent lives in this relentless and unjustifiable violence is iniquitous and painful," he said.

Mr Thomas called for delegates at the forthcoming international security conference in Abuja to work on a joined up strategy to tackle the insurgency.

"It is vital that sufficient and well-resourced troops are urgently relocated to troubled areas in order end this appalling cycle of violence and impunity," he said.

"Justice is also imperative for lasting peace, and the perpetrators of these crimes must be held to account."