Two car bombs have exploded in the northern Nigerian city of Kaduna, killing several people and injuring many others, officials say.The Nigerian Red Cross said six people had died. The emergency services had earlier put the number of dead at 18.The blasts, which caused extensive damage, happened close to restaurants, a hotel and at least one church.The area has been the scene of a religious conflict in recent years that has claimed hundreds of lives.There had been warnings of attacks in the region over Easter.Many of the dead are thought to be motorcycle taxi drivers and beggars.Witnesses say debris was thrown dozens of metres from the centre of the blast.No one has yet admitted carrying out the bombing, but the BBC's correspondent in Nigeria, Mark Lobel, says the radical Islamist group Boko Haram recently said it would carry out attacks in the area over the Easter holiday.Local Christian groups have speculated that the bombers were targeting a nearby church, but that heavy security meant they detonated their explosives in a nearby area instead.