Maiduguri - Gunmen opened fire on a church service in the northeast Nigerian village of Attangara, killing nine people, police and a witness said on Monday.
The village is in the Gwoza hills, near the Cameroon border, and the main stronghold of radical Islamist sect Boko Haram which has killed civilians on an almost daily basis since stepping up its campaign of violence earlier this year.
"As we were holding service, we started hearing gunshots and everybody fled, some through the windows, and ran into the bush," resident Matha Yohana said of Sunday's attack. A police source said nine were killed in the assault.
"More than 10 of them were riding motorcycles and one car," she said, adding some local vigilantes had pursued the attackers, killing four of them and detaining three.
Nigeria's military said on Monday it had arrested a suspect it believes was behind a bomb attack that killed 18 people watching football on television in the northeast the previous day.
There has been no claim of responsibility for the blast that also wounded 19 people in Kabang town in Adamawa state, a stronghold of Islamist militant group Boko Haram whose struggle for an Islamic state is centred in the northeast.
"A key suspect in the terror bomb explosion that rocked Kabang Community in Mubi, Adamawa State ... has been arrested by troops who cordoned (off the) area in swift response to the explosion," Defence spokesman Brigadier General Chris Olukolade told Reuters by telephone from the capital Abuja.
The final toll was 18 killed, 19 wounded, he added. Initial reports had put the death toll at 14.
Adamwa state has been under a state of emergency declared by the government in May last year, with military patrols and an offensive meant to dismantle the Boko Haram network.
Boko Haram, whose violent struggle for an Islamic state in religiously-mixed Nigeria has killed thousands in the past five years, has set off several bombs across north and central Nigeria since April.
The sect is still holding 219 girls abducted from a secondary school on April 14. Nigeria has accepted help from foreign powers such as the United States to try to free them.
Nigeria's president ordered "a full-scale operation" against Boko Haram on Thursday, seeking to reassure parents of the kidnapped girls that their daughters would be freed.
Boko Haram, seen as the main security threat to Africa's biggest economy and top oil producer, has killed thousands since launching an uprising in 2009.