With the February 2006 al-Askari mosque bombing in Samarra, the violence escalated into a civil war which lasted from 2006 until the start of 2008. In this war, sectarian militias engaged in sectarian cleansing activities. Although exact numbers of casualties are uncertain, it is estimated that more than 20,000 civilians were killed in 2006 alone. By the start of 2008, tens of thousands of Iraqi civilians had been killed with about 4 million being displaced. Especially, the capital of Baghdad was hard hit as the city came to be rearranged on a sectarian basis. Former mixed neighbourhoods came to be ruled by sectarian militias who drove out everyone with another sectarian affiliation. Besides sectarian killings by death squads, the violence also included kidnappings for ransom payments and torture in secret detention centres ran by militias.