A suicide bomb claimed by the ISIS terrorist organization killed at least seven people, including two police, when it exploded on Monday near a Shi'ite Muslim procession in a northern Baghdad neighbourhood, police and medical sources said.The explosion in Shaab, which the sources said left 23 wounded, was one of a relatively small number of attacks reported in Iraq over the weekend as Shi'ites across the Muslim world marked the holy day of Ashura.The annual ritual, which commemorates the slaying of Prophet Mohammad's grandson Hussein in AD 680, has become a flashpoint for attacks over the last decade.ISIS, the militant group that seized swathes of northern and western Iraq last year, claimed responsibility for the blast in a statement distributed online by supporters.The group said the target was "rejectionists" - a derogatory term it uses to refer to Shi'ite Muslims. It said 20 people were killed and 40 wounded.Reuters could not verify the authenticity of the statement.In addition to such attacks, Iraq is gripped by a sectarian conflict mostly between Shi'ites and Sunnis that has been inflamed by the rise of the ultra-hardliners of ISIS.A spokesman for the Interior Ministry confirmed that the blast, caused by an assailant wearing an explosive vest, had resulted in several deaths and injuries.Security during Ashura has been tight in recent years since suspected al Qaeda suicide bombers and mortar fire killed 171 people during the rituals in Kerbala and Baghdad in 2004, though attacks have continued.