An Al-Qaeda suspect killed two police guards on Sunday in an unsuccessful attempt to escape from custody while in hospital, a medic said. The suspected militant managed to get hold the weapons of two of his guards and killed them. He then exchanged fire with the three remaining guards, the medic at the Republican Hospital said. 'Smoke was seen coming out of his room,' and he handed himself in, the medic added. A source close to the police who requested not to be named said the suspect is believed to have joint US-Yemeni citizenship. Yemeni authorities intensified their campaign against the country's Al-Qaeda branch after it claimed a botched Christmas Day bombing attempt on a US passenger plane en route for Detroit. On Thursday, a security official said 11 men were arrested in the capital Sanaa on suspicion of plotting attacks for Al-Qaeda. Al-Qaeda militants have previously targeted Western embassies in the city. 