A huge explosion has rocked central Baghdad. A car bomb went off at a busy intersection, just as a foreign security convoy was driving past. At least 17 people, including four foreigners, are said to be dead. Over 30 others were injured. Some reports say the blast happened outside a school that was in session.Security contractors regularly move around in high profile convoys of four-wheel-drive vehicles. They are a frequent target for insurgents. Today’s blast is the latest incident in a fresh wave of violence that has erupted since the announcement of Iraq’s new government last month. On Friday, a suicide car bomb hit a crowded vegetable market in the town of Suwayra, south of the capital. In a newly-revised death toll, officials say 31 people were killed.