A bomb attack targeting Shiite pilgrims travelling on foot to a shrine city in central Iraq on Wednesday killed 17 people,including a woman and three children,a senior health official said. The blast struck on the outskirts of Karbala,110 kilometres south of Baghdad,the provincial health official told AFP,adding that 116 people wounded were being treated at two hospitals in the city. He described the incident as an explosion. It was not immediately clear if it was a suicide attack or a roadside bomb. The victims had been travelling on foot from Hilla in Babil province to Karbala to observe Friday's Arbaeen rituals. The rituals mark 40 days after the Ashura anniversary commemorating the slaying of one of Shiite Islam's most revered figures,Imam Hussein,by the armies of the Sunni caliph Yazid in 680 AD. Tens of thousands of Shiites,including many from neighbouring Iran,make their way annually at Arbaeen to pay homage at Imam Hussein's shrine in Karbala,considered one of the holiest places in Shiite Islam. In Baghdad on Monday a female suicide bomber blew herself up among a crowd of pilgrims who were making their way to Karbala for the ceremonies,killing at least 41 people. In recent months insurgents had appeared to direct their attacks away from religious targets to government buildings in Baghdad.