A suicide bomber on a bicycle killed 28 Iraqi policemen doing their morning exercises at their base north of Baghdad on Monday, police said, in one of the deadliest strikes on security forces in months.

The bomber entered the base in the volatile Diyala province and blew himself up amidst members of a rapid reaction force. 

A shopkeeper whose store is close to the base said he had seen a man riding a bicycle slip through a gap in the concrete wall surrounding the compound and heard a huge blast seconds later that threw a cloud of dust into the air. At least 20 people were wounded in the attack, including a woman and a child, police said.  No group claimed immediate responsibility for the Baquba bombing.