Najaf car bomb kills at least 10

Police said the blast happened about 300m (330 yards) from the Imam Ali shrine, which is among the world's most sacred sites for Shia Muslims.

It comes amid deadlock over the formation of a government, thought to be partly responsible for fuelling an increase in sectarian violence.

Tensions have risen since the bombing of a key Shia shrine in February.

The attack on the shrine in Samarra, north of Baghdad, set off a wave of violence between Iraq's Shia and Sunni communities.

Thursday's blast is the first serious bomb attack in the holy city of Najaf in many months.

Women

Witnesses told the Associated Press news agency more than 10 cars were destroyed by the bomb, which exploded in a car park near the city's massive cemetery - one of the largest in the world.

Four of those killed were women, according to the head of Najaf mortuary.

Iraqi security forces have sealed off the centre of the city and ordered people to leave the area for fear other bombs may be hidden there, the AP news agency reported.

Najaf is Iraq's holiest city for Shias, and was the scene of fighting in 2004 between US forces and those loyal to radical Shia cleric Moqtada Sadr.

Pressure

The on-going violence is increasing the pressure on the Prime Minister, Ibrahim Jaafari, to step down.

Thursday's attack has led to renewed calls for him to resign, but Mr Jaafari is refusing to do so.

"I will stick to the result of the democratic process and reject any bargaining over it," he said.

But he added: "If parliament asks me to withdraw then I will."

Iraq's political parties have been wrangling over forming a new government for four months.

Kurdish and Sunni Arab parties rejected the ruling Shia-led bloc's nomination of Mr Jaafari as prime minister and have threatened to boycott a government unless he withdraws.

The delay in forming a government is thought to be partly responsible for fuelling the increasing violence.