At least 28 people have been killed and 50 wounded in a suicide blast in southeast Baghdad, security officials have said.

The blast targeted a police patrol in the Karrada district on Thursday and the dead included at least 13 policemen, the interior ministry said.

The police were said to be helping to distribute relief supplies to displaced Iraqis at the time of the attack.

A medic at the nearby Ibn al-Nafis hospital confirmed the casualties.

Security has improved dramatically in Iraq over the past two years, but attacks targeting the police are still common in some parts of the country, including the capital.