At least 500 prisoners escaped when militants assailed two prisons in Iraq, sparking fierce clashes that lasted about 10 hours and killed dozens of people, MPs said on Monday.

At least 500 prisoners escaped when militants assailed two prisons in Iraq, sparking fierce clashes that lasted about 10 hours and killed dozens of people, MPs said on Monday.

"About 500 prisoners escaped from Abu Ghraib prison," Hakem al-Zamili, a member of parliament's security and defense committee, said.

Zamili said that, according to his knowledge, no inmates escaped from the prison in Taji, the second that was attacked.

But MP Shwan Taha, also a security and defense committee member, said in an online statement that between 500 and 1,000 inmates escaped from the two prisons.

The coordinated attacks on Taji, north of Baghdad, and Abu Ghraib, west of the Iraqi capital, were launched on Sunday night and raged until Monday morning, officials said.

Officials said at least 20 members of the security forces were killed and 40 wounded in the attacks.

And the justice ministry's spokesman said that 21 inmates were killed and 25 wounded during rioting at the prisons, without specifying whether they were bystanders or taking part in the fighting.

The attacks on the prisons came a year after Al-Qaeda's Iraqi front group announced it would target the Iraqi justice system.

"The first priority in this is releasing Muslim prisoners everywhere, and chasing and eliminating judges and investigators and their guards," said an audio message attributed to the group's leader, Abu Bakr al-Baghdadi, in July last year.

Prisons in Iraq are periodically hit by escape attempts, uprisings and other unrest.