KANO, Nigeria: Nigeria’s Boko Haram Islamists have ruled out talks with the government and threatened new attacks in Africa’s most populous country, rocked by an insurgency that has killed more than 200 already this year.

Residents in the northern city of Kaduna said the group, which has often targeted the police, may have struck again late Saturday when gunmen on motorcycles shot dead a policeman.

Police confirmed the killing early Sunday, but said the attackers were trying to steal the officer’s motorcycle.

Kaduna resident Rabiu Tukur disputed that account. “They did not make any attempt to take his motorcycle, which raised the fear that the attackers could be members of Boko Haram,” he said.

The group’s deadliest ever strike came Jan. 20, north of Kaduna, in Nigeria’s second city of Kano, where a coordinated set of gun and bomb attacks killed at least 185 people, highlighting the Islamists’ renewed strength.

Heavily criticized amid the escalating violence, President Goodluck Jonathan urged the group to enter dialogue in a media interview this week.

But Jonathan’s call for talks was “not sincere,” purported Boko Haram spokesman Abul Qaqa told journalists Sunday by telephone in the northeastern city of Maiduguri, regarded as the group’s stronghold.

“We don’t think dialogue is possible under the current situation,” he added.

If captured members of the group were not released, it “will launch attacks in Sokoto similar to the big Kano attacks,” Qaqa warned.

Sokoto is a northwestern city which is the capital of a state of the same name.

Kano, Nigeria’s second city and north of Sokoto, had escaped the worst of Boko Haram’s violence, but since the deadly Jan. 20 attacks the mainly Muslim northern hub has been put on edge.

The military and police guarded the city’s churches Sunday, and worshippers were frisked before being allowed to enter, according to an AFP reporter.

Crowds were thin and services ended earlier than usual because of security concerns, worshippers told AFP.

In a leaflet distributed around the city overnight, Boko Haram urged the city’s residents to persevere as the group continues its campaign against Nigeria’s security forces. Boko Haram is aware of “the atmosphere of inconvenience our operations have thrown people into,” the leaflet said.

The document’s content was described as a message from purported Boko Haram chief Abubakar Muhammad Shekau.

Boko Haram’s intensified violence has shaken Africa’s top oil producer, which is divided between a mainly Muslim north and mainly Christian south.