The Boko Haram insurgency draws more international criticism.

Sect Claims Multiple Attacks on Nigerian City

At least 138 people have died since Sunday in sect-related violence in Nigeria, officials say, as the government fails to corral rising sectarian attacks that have fanned religious tensions in Africa's most populous nation.

An email statement attributed to the radical Islamist sect Boko Haram and obtained by The Associated Press on Thursday said it launched multiple attacks in the city of Damaturu, which authorities say killed at least 40 people.

"We assure all that the success of the Damaturu operation is really a sign that very soon Allah will give us the chance of overthrowing this unjust and heathen government and replacing it with an Islamic system which is just," the statement said in the local Hausa language.

It came two days after the group claimed responsibility for a trio of church bombings in the religious flashpoint state of Kaduna that left at least 21 dead, according to rescue officials. The bombings sparked reprisals that have raised the overall toll to at least 98 dead, a rescue official involved in rescue efforts said Wednesday. He spoke on condition of anonymity, saying he was not authorized to speak to journalists.

The attacks, which occurred more about 450 miles (720 kilometers) apart, seem to have been calculated to increase religious tensions in the West African nation, which is almost evenly divided between Muslims and Christians.

Sunday's attacks occurred while Christian church services were ongoing in a state with a history of religious violence. The first two suicide bomb attacks occurred within about 10 minutes of each other in different part of the city of Zaria. Thirty minutes later, a third attack targeting a church rocked the nearby city of Kaduna.

A day after the trio of church bombings Sunday, the sect struck churches in the city of Damaturu in Yobe State, 450 miles (720 kilometers) north of Kaduna. An AP reporter counted four bombed churches. He saw the gate of a police station punctured by bullets and a crumbling police outpost. Assailants also had bombed five primary schools, said Yobe State police chief Patrick Egbuniwe.Churches have been increasingly targeted by violence in Nigeria, and it was the third weekend in a row that Boko Haram has claimed responsibility for church attacks in central and northern Nigeria.The reprisals that have pitted Muslims and Christians against one other in Kaduna state continued Thursday. The sustained attacks have increased pressure on Nigeria's security forces.

"The terrorists are trying to show they can't be stopped," said Egbuniwe, as gunfire echoed in the streets of Damaturu. In the face of growing sectarian violence, the Nigerian government's response has drawn criticism. Nigerian President Goodluck Jonathan traveled to a U.N. environmental conference in Rio de Janeiro, Brazil, as the crises in Kaduna state spiraled and Damaturu remained paralyzed by a round-the-clock curfew.

At home, Christian and Muslim leaders are worried about the security of the faithful. The Christian Association of Nigeria on Thursday called the government's response to the violence "cavalier."

"Since these terrorist acts began, nothing the (president) has done has been re-assuring that the end to this spate of bombings and gun attacks is in sight," the group said in a statement.

The Muslim umbrella organization Jama'atu Nasril Islam has said the performance of security forces needs "serious introspection."

"Why should an innocent traveler ... passing through Kaduna be burned alive just because he is Muslim?" the statement said. Meanwhile, the Boko Haram insurgency drew more international criticism.

Pope Benedict XVI appealed on Wednesday "to those responsible for the violence so that the spilling of blood of so many innocent (people) stops immediately."

The U.S. State Department said Thursday that three Boko Haram leaders would now be regarded as international terrorists in an effort to reduce the sect's ability to launch attacks.