At least five people were killed and 24 were injured on Sunday in a suicide attack at a security checkpoint close to the southern Iraqi city of Najaf, a security source said.A group of armed men attacked a security checkpoint and detonated explosives-laden vests when the officers tried to repel them, Efe news agency reported.The security source said the armed militants were travelling in a modern vehicle when they carried out the attack on a checkpoint in the district of Al-Qadisiyah, some 70 km southwest of Najaf, a Shiite holy site some 240 km from Baghdad.The toll could go up, the source said, adding that the attack also caused material damage.No group has so far claimed responsibility for the attack. However, the Islamic State (IS) terror group, in most cases, is responsible for such suicide bombings targeting Iraqi security forces as well as crowded areas, including markets, cafes and mosques across the country.