KANO, Nigeria : Nigeria's Boko Haram was suspected Sunday of killing a Muslim cleric who had criticised the Islamic extremist group, and of shooting dead a Christian preacher, in the latest violence to hit northern Nigeria.

The deaths came after seven people were killed by a roadside bomb in a border area of the remote northeast, which has seen mounting militant activity in recent months, and heavy casualties last weekend. The first attack happened when unidentified gunmen shot at Muslim cleric Adam Albani's car at about 10:30 pm (2130 GMT) on Saturday in Zaria, as he drove home from teaching a theology class.

Local resident Mohammed Usman said Albani's wife and son were hit, while the gunmen appeared to have dragged the cleric from the car and shot him at close range.  "We kept hearing gunshots very close to our homes and later we heard the sound of a car retreating and when we later came to the scene we found Sheikh Albani lying outside the car with lots of bullet holes on him," he added.

"He was still alive but his wife and a child she was holding in the front seat were already dead while the rest of the children sitting in the back seat were unharmed."

Albani's brother Kaburu Adam said the cleric, who had criticised the group and given his support to the Nigerian military campaign against them, died shortly after he was admitted to hospital.

Separately, gunmen killed a pastor in an attack on a church in Sabon Garin Yambdula, in the Madagali area of Adamawa state late on Friday.

Ten people tried to repel the attack with hunting rifles, said Madagali local government chairman Maina Ularamu.

The attackers made off with four cows and also killed two goats, said Ularamu, who declined to say whether Boko Haram fighters were responsible.

But the attack came after 26 people, most of them worshippers, were killed in a Roman Catholic church in Waga Chakawa, also in Madagali, last Sunday.

"All we know is that the gunmen were not soldiers, although they were dressed in military uniform, because some of them wore bathroom slippers instead of boots," he said.

Others had their faces covered, he added.

Zaria, a predominantly Muslim city with a reputation as a centre for Islamic and Western scholarship, has not been known as a major hotbed of Islamist activity.

Adamawa was one of three northeastern states placed under emergency rule in May last year but has been relatively calm in recent months and has even led to calls for the special measures to be lifted.

But fears grew among locals in Zaria of Islamist cells operating in the city, when a French engineer escaped from his captors last November.

Albani's theology class was in the Tudunwada area of Zaria, where soldiers had carried out raids on two suspected militant hideouts in the past.

Nigeria's new chief of defence staff is from Adamawa and said during his inauguration last month that he wanted a swift end to the insurgency.

Some analysts believe Boko Haram may have interpreted that as a challenge.

Thousands of people have been killed since 2009 in attacks blamed on Boko Haram, which want to create an Islamic state in northern Nigeria.

On Friday, seven people were killed and three others seriously injured when their bus ran over a home-made bomb near Kuthra village in the Gwoza area of Borno state.

Boko Haram has scaled up deadly attacks in the border area with Cameroon in recent months and police blamed the group for planting the device.

Gwoza is some 90 kilometres (55 miles) by road from Kawuri, where last Sunday at least 52 people were killed when suspected Islamist gunmen stormed a busy market.