BAGHDAD  - At least 18 Iraqis heading to Karbala for a religious festival were among 22 people killed on Thursday as a spate of bomb blasts rocked Iraq, security officials said. At least 17 were killed in a double attack by two women suicide bombers who blew themselves up among a crowd of Shia pilgrims heading to the city, police Lieutenant Kazem al-Khafaji in Babil province said. The women detonated their explosives-packed vests 50 yards apart and at a five-minute interval in Iskandiriyah 60km south of the capital, Khafaji added. The twin suicide attack left at least 40 more wounded, 13 of whom were in a serious condition, Khafaji added. Earlier, another Iraqi was killed and seven others wounded by a roadside bomb in Baghdad's commercial district of Karrada as they set off for Karbala, around 110km) south of Baghdad for Sunday's festival. Another explosion killed a policeman and wounded five of his colleagues near a checkpoint in the Zafraniya district of southern Baghdad set up to search pilgrims heading south. In other violence, a car bomb targeting a police patrol near the restive city of Baquba, about 60km north of Baghdad, killed two policemen and wounded six, security officials said. The Defence Ministry said that on Tuesday the Iraqi army discovered dozens of houses that had been booby-trapped with explosives by Al-Qaeda jihadists in the same area " about 10 kilometres southeast of Baquba. Also near Baquba, a bomb hidden in a field killed a 10-year-old girl, a security official said. On July 29, some 50,000 Iraqi soldiers and police launched a major push against Al-Qaeda and other insurgents in Diyala, which commanders describe as Iraq's most dangerous province. The Iraqi military imposed a curfew on Baquba, capital of Diyala, on Tuesday after a suicide bomb attack wounded the province's governor.