(A victim of a bombing at Shalom Church awaits treatment in a hospital, in the northern Nigerian city of Kaduna June 17, 2012. REUTERS/Stringer )

Explosions at three churches in Nigeria’s northern Kaduna state killed 19 people on Sunday. Here is a look at attacks against Christian targets in Nigeria.

* OVERVIEW:

- The Islamist group Boko Haram, which says it is fighting to reinstate an Islamic caliphate in mostly Muslim northern Nigeria, has stepped up deadly bombings and shootings against Christian places of worship this year.

- This follows its high profile strikes against churches on Christmas Day in December 2011 and on Christmas Eve in 2010.

- Experts have said the anti-Christian attacks by the sect, which also often targets security forces and establishment figures, appear partly aimed at trying to ignite sectarian conflict in the country, whose 160 million people make it Africa’s most populous nation and are split roughly evenly between Christians and Muslims.