KADUNA, Nigeria -- Suicide bombers killed 21 people in attacks on three churches during Sunday services, exacerbating religious tensions in a West African nation that is almost evenly divided between Muslims and Christians.

Authorities arrested one of the bombers who survived, said Kaduna State police chief Mohammed Abubakar Jinjiri, but he declined to say who police suspect was responsible for the bombings.

It was the third Sunday in a row that deadly attacks have been carried out against Christian churches in northern Nigeria. No one immediately claimed responsibility, but suspicion fell on the radical Islamist sect Boko Haram because it took responsibility for two earlier weekend assaults.

Boko Haram is waging an increasingly bloody fight with security agencies and the public in Nigeria. More than 560 people have been killed in violence blamed on the sect this year alone, according to an Associated Press count.

On Sunday, the suicide bombers drove explosive-laden cars to the gates of two churches in different parts of the city of Zaria and detonated them within minutes of each other. A similar attack targeted a church in the city of Kaduna about half an hour later about 9:25 a.m., police said, prompting reprisals by Christian youths.

The attacks in the northern state of Kaduna killed 21 people and wounded at least 100, said an official who works with a relief agency involved in rescue efforts. He spoke on condition of anonymity because he wasn't authorized to speak to journalists.

It wasn't immediately known whether the reprisal attacks caused casualties in the religious flash point state, but hundreds of people have died in previous retaliatory violence there.

"The Boko Haram group's intention in bombing the churches is to attract reprisal attacks from the Christians, draw the battle line between Muslims and Christians and, [by doing so], get moderate Muslims to support them," said Shehu Sani, the president of the Kaduna-based Civil Rights Congress of Nigeria.

In Italy, the Vatican decried what it called systematic attacks against Christian churches. Vatican spokesman the Rev. Federico Lombardi said in a statement that the "systematicness" of the attacks against Christian places of worship on a Sunday is "horrible and unacceptable" and reflects "an absurd design of hatred."

Within an hour of the Kaduna city attack, an Associated Press reporter saw billows of smoke over a mosque in a predominantly Christian part of the city. Some Christian youths quickly mounted illegal roadblocks and were seen harassing motorists.

A motorcycle taxi rider in that same neighborhood lay seriously hurt and bleeding by the road side. Motorcycle taxi riders there are often presumed to be Muslim and become easy targets during reprisal attacks by Christians.

"The Christians can't see Boko Haram," said Sani, "so they'll retaliate against Muslims."

A Newsday analysis shows the number of referees and umpires has declined 25.2% in Nassau and 18.1% in Suffolk since 2011-12. Officials and administrators say the main reason is spectator behavior. NewsdayTV's Carissa Kellman reports. Credit: Newsday Staff

Updated 37 minutes ago A Newsday analysis shows the number of referees and umpires has declined 25.2% in Nassau and 18.1% in Suffolk since 2011-12. Officials and administrators say the main reason is spectator behavior. NewsdayTV's Carissa Kellman reports.

A Newsday analysis shows the number of referees and umpires has declined 25.2% in Nassau and 18.1% in Suffolk since 2011-12. Officials and administrators say the main reason is spectator behavior. NewsdayTV's Carissa Kellman reports. Credit: Newsday Staff

Updated 37 minutes ago A Newsday analysis shows the number of referees and umpires has declined 25.2% in Nassau and 18.1% in Suffolk since 2011-12. Officials and administrators say the main reason is spectator behavior. NewsdayTV's Carissa Kellman reports.

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