A suicide bomber on Tuesday rushed into a crowd of police recruits in central Iraq and detonated his explosives-laden vest, killing at least 25 people and wounding 40, the local police chief said.

Lieutenant Colonel Ahmed Khalifa said the attack targeted a crowd of young Iraqis at a police recruiting centre in Jalawla, 150 kilometres north of Baghdad.

Most of those killed had been waiting to join the police, he added.

Earlier, officials said a man wearing an explosives-laden vest arrived by car and was stopped by police. He then leapt from the car and ran into the crowd where he detonated his bomb.

Jalawla is in Diyala province, considered to be one of the country's most dangerous.

It sees regular attacks by al-Qaida-linked groups targeting Sahwa or "Awakening" units of Sunni former fighters who have turned against the jihadists and are now financed by the American military.