A suicide bomber struck police lined up at the entrance of the main police academy in Baghdad on Sunday, killing 30 people and wounding 61, officials said. The bloodiest attack in weeks came as the US military said 12,000 American and 4,000 British troops will leave Iraq by September. Police academies across Iraq have come under repeated attack as Al-Qaeda and other insurgents continue to target security forces around the country. Fifteen people died and more than 45 were wounded in two blasts at the Baghdad academy on Dec. 1. On Sunday, the bomber on a motorcycle activated his explosive vest as he ploughed into the crowd on busy Palestine Street in central Baghdad, a mainly Shiite area of the capital. Haitham Fadhel said he was standing in one of three lines of recruits arriving for their first day of special guard training courses at the academy. “We were feeling secure as we were waiting in a well-guarded area,” he said. “Before the explosion occurred I heard a loud shout saying ‘Stop, stop, where are you going?' Seconds later, a huge explosion shook the area.” The 24-year-old recruit from the mainly Shiite neighborhood of New Baghdad was knocked unconscious and was wounded by shrapnel. He said he was lucky because the bomber struck a different line, but two of his friends were killed. “I am just wondering how a big security breach can occur in such a secured area,” Fadhel said. “I came here to get a job after four years of staying at home even though I graduated from Oil Institute ... but it seems that I have no luck.” The blast was a bloody reminder of the ability of insurgents to defy security improvements and stage dramatic attacks as the US begins to draw down its forces. Maj. Gen. David Perkins announced Sunday that the troop withdrawals will reduce US combat power from 14 brigade combat teams to 12 along with some supporting units. The US also plans to turn over 74 facilities and areas under its control to the Iraqi military by the end of March as part of the drawdown. President Barack Obama has decided to remove all combat troops by the end of August 2010 with the remaining forces leaving by the end of 2011. The 4,000 British troops due to leave are the last British soldiers in Iraq. The US withdrawal will at first be very gradual, leaving most troops in place for parliamentary elections at the end of this year. There are currently about 135,000 US troops in Iraq. Remaining American forces will be repositioned in coordination with Iraqi authorities to ensure the most dangerous areas in Iraq are protected, Perkins said. Some 258 Iraqis were killed in violence last month, a sharp rise from the previous month that saw the lowest casualty figures since the US-led invasion of March 2003, according to government statistics. But Perkins insisted violence has dropped more than 90 percent and was at its lowest level since the summer of 2003, claiming a recent spate of high-profile attacks, including Sunday's bombing, was evidence of an increasingly desperate Al-Qaeda in Iraq. “Al-Qaeda and other terrorists are still active,” he said, adding insurgents appear to be stepping up attacks to derail recent progress by the Iraqi government in holding provincial elections and in reaching a new security agreement with the United States. “It's indicative that Al-Qaeda feels threatened. They're feeling desperate. They want very much to maintain relevance,” he said.