Violent clashes between Christians and Muslims in Nigeria's north flared again Wednesday, bringing the death toll from four days of unrest close to 100.

The clashes took place despite a round-the-clock curfew in the cities of Kaduna and Damaturu. Witnesses reported a large number of soldiers patrolling the streets.

The wave of unrest began Sunday, when the Islamist militant group Boko Haram attacked three Christian churches in Kaduna state. The suicide bombings killed at least 21 people and sparked reprisal attacks by Christians against Muslims that reportedly killed another 52 people in Kaduna.

On Monday, suspected Boko Haram militants attacked police and security targets in Damaturu. Shootouts between militants and security forces continued into Tuesday and left at least 40 people dead.

Authorities blame the unrest on both Christians and Muslims.

Nigeria has a history of sectarian violence, especially in the country's Middle Belt, where the mainly Muslim north meets the predominantly Christian south.

Boko Haram says it is fighting for an Islamic state and does not recognize the Nigerian government or the constitution.

Meanwhile, Nigerian President Goodluck Jonathan has come under fire for leaving the country to attend the environmental conference in Brazil amid the unrest.

The opposition Action Congress of Nigeria said the president's decision was a reflection of “insensitive and confused leadership.”

Northern leaders continue to call for dialogue, and not force, to end the Boko Haram insurgency. Although recent efforts at mediated talks between the government and the sect failed, Nigerian officials say those efforts will continue because it is “never too late” to talk.