A suicide car bomber has launched an attack in the fortified Green Zone in Baghdad. One person was killed and at least four others have been wounded.

The blast struck a checkpoint near the headquarters of the caretaker Prime Minister Iyad Allawi's offices, a building that has been targeted by guerrillas before.

Elsewhere, the bodies of 50 people have been found in the Tigris River south of Baghdad. The announcement was made by Iraqi President Jalal Talabani.

The bodies are believed to be those of hostages held in a town near Baghdad earlier this week.

At the weekend, Shi'ite officials said that some 50 people had been taken hostage by Sunni militants in the town of Madaen, south of Baghdad, and were threatened with death.

Iraqi security forces raided the town earlier this week, but said they had found no evidence that anyone had been taken hostage or that there were any gunmen in the town.

Later, Shi'ite officials said that dozens of bodies had been found in the Tigris River.

However, residents and police in the area said they had not seen any bodies.

Meanwhile, in the town of Haditha, north-west of Baghdad, at least 19 men were found dead at a football stadium.

They had apparently been lined up against a wall and shot.

The interior ministry said they were Iraqi soldiers who had been abducted by insurgents while travelling to Haditha.