The death toll in a suicide attack carried out on Sunday against an Iraqi security checkpoint close to Iraq's Najaf city has increased to seven, including five policemen, according to the local police command.The Islamic State terror group claimed responsibility for the attack through its affiliated Amaq news agency, claiming that at least 100 people were killed in an attack that was carried out by five suicide bombers, EFE news reported.According to a security official, a group of armed assailants attacked a security checkpoint and detonated explosive-laden belts they were wearing when the officers tried to repel them.The source said armed assailants had been travelling in a modern vehicle when they carried out the attack on a checkpoint in the district of Al-Qadisiyah, some 70 kilometres (43.5 miles) southwest of Najaf, a Shiite holy site some 240 km from Baghdad.This attack came a day after Baghdad's double bombing, in which at least 28 people were killed.