(Reuters) - At least 52 people were killed in religious rioting sparked by three suicide bombings against churches in northern Nigeria, where the dead were on Monday piled up in mortuaries and cemeteries in the city of Kaduna.
Following is a look at the worst of the religious and ethnic violence in Nigeria since 2000:
2000 - Thousands killed in northern Nigeria as non-Muslims opposed to the introduction of sharia (Islamic law) fight Muslims who demand its implementation in the state of Kaduna.
September 2001 - Christian-Muslim violence flares after Muslim prayers in the city of Jos in central Nigeria, with churches and mosques set on fire. At least 1,000 people are killed, according to a report in September 2002 by a panel set up by the government of Plateau state, which includes Jos.
November 2002 - Nigeria abandons Miss World contest in Abuja. Decision follows death of at least 216 people in rioting in Kaduna, 200 km (125 miles) northwest of Jos, after newspaper article suggests Prophet Mohammad would probably have married one of the Miss World beauty queens if he were alive today.
November 2008 - Clashes between Muslim and Christian gangs triggered by disputed local government election kill at least 700 people in Jos, according to U.S.-based Human Rights Watch.
July 2009 - More than 800 people are killed in five days of violence between members of Boko Haram and security forces in states across northeast Nigeria. The sect’s leader Mohammed Yusuf is captured and dies in police custody on July 30.
January 2010 - Hundreds are reported killed after clashes between Muslim and Christian gangs in Jos, most by gunfire. Police estimate death toll at 326, although some community leaders put the figure at more than 400.
March 2010 - Hundreds of people are killed in clashes between Muslim pastoralists and Christian villagers in the mostly Christian villages of Dogo Nahawa, Zot and Ratsat just south of Jos. Plateau State Commissioner for Information Gregory Yenlong says more than 300 people died.
December 2010 - At least 80 people are killed in December 24 bombings as well as in clashes two days later between Muslim and Christian youths in Jos.
January 2011 - Human Rights Watch says more than 200 people killed in violence over preceding month, many hacked to death in attacks on villages, and reprisal killings in Plateau state.
August-September 2011 - At least 70 people killed in clashes in central Plateau state. Violence starts when Christian youths attack Muslims gathering to celebrate end of Ramadan in Jos.
November 2011 - At least 65 people killed in northeast city of Damaturu when Islamist insurgents bomb churches, mosques and police stations. Boko Haram claim responsibility.
December 2011 - Boko Haram claims responsibility for bomb attacks across Nigeria on Christmas Day, including one at a church near Abuja that kills at least 37 people.
January 2012 - Bomb attacks and gun battles in Kano kill 186 people, Boko Haram’s most deadly attack to date.
— Human Rights Watch says in a report that Boko Haram has killed at least 935 people since 2009.
— Gunmen open fire on church service in Nasarawa in northern Gombe state, killing six people on Jan 5. The attack follows a warning from Boko Haram that Christians have three days to leave majority Muslim northern Nigeria or they will be killed. The next day gunmen open fire on Christian mourners in Mubi in Adamawa state, killing 18.
February 2012 - A suicide bomber strikes a church in Jos, killing two in an attack claimed by Boko Haram. Christian youths beat two Muslims to death in revenge.
March 2012 - Another suspected suicide bomber attacks a Catholic Church in Jos, killing at least three people. Reprisal attacks against Muslims by Christian youths kill at least 10.
April 2012 - A car bomb explodes on Easter Sunday near a church in Kaduna, killing 36 people.
June 2012 - Three gunmen attack the congregation in Biu Town, in Borno state. In Jos, the Christ Chosen Church is attacked wounding 41 people. Youths attack bystanders in retaliation, killing two. Boko Haram claim both attacks.
— Following suicide attacks on three churches on June 17 which kill 19 people, 52 others are killed in revenge.
Reporting by David Cutler, London Editorial Reference Unit