Militants attacked two Iraqi prisons, including notorious Abu Ghraib, with mortars, bombs and gunfire, freeing at least 500 inmates in assaults that cost more than 40 lives, officials said Monday.

The coordinated attacks on the prison in Taji, north of Baghdad, and Abu Ghraib, west of the capital, were launched on Sunday night and triggered fighting that raged for around 10 hours, officials said.

Abu Ghraib prison, already infamous as a centre for the torture of opponents of now-executed dictator Saddam Hussein's regime, gained further notoriety in 2004 when graphic pictures emerged showing prisoners being humiliated and abused by their US guards.

A frenzy of comments posted on social media, including some Twitter accounts apparently operated by jihadists, claimed that thousands of prisoners had escaped.

The two prisons had held around 10,000 inmates between them, an interior ministry official said.

"About 500 prisoners escaped from Abu Ghraib prison," Hakem al-Zamili, a member of the parliamentary security and defence committee, told AFP.

He said the escaped prisoners were "terrorists" and that, to his knowledge, no inmates managed to break out in Taji.

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

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 21 inmates were killed and 25 wounded in rioting at the prisons.

It was not immediately clear how many of the militants who attacked the prison were killed, wounded or captured.

The attacks were launched at around 9:30 pm (1830 GMT) on Sunday when the militants fired mortar rounds at the prisons.

Car bombs were detonated near the entrances to the prisons, while three suicide bombers attacked the Taji prison, a police colonel said. Five roadside bombs also exploded near the prison in Taji.

Fighting continued throughout the night and the situation was eventually brought under control on Monday morning, according to the colonel.

The interior ministry had issued a statement before midnight (2100 GMT) on Sunday saying the attacks had already been foiled.

But a statement released by the ministry on Monday said that prisoners had escaped and were still on the loose.

"This incident resulted in the escape of a number of prisoners in the Abu Ghraib prison" but none from that in Taji, the statement said, adding that an initial investigation indicated that some prison guards were culpable.

The attacks on the prisons came a year after Al-Qaeda's Iraq front group announced it would target the country's 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 last year.

Prisons in Iraq have previously been hit by escape attempts, uprisings and other unrest.

Deadly violence also hit security forces in northern Iraq on Monday.

A suicide bomber blew up a vehicle near an army patrol in the city of Mosul, killing 12 people and wounding 16, while a bomb killed a soldier near the city.

In the city of Kirkuk, gunmen shot dead Abdullah Sami al-Asi, a provincial councillor and deputy head of the province's security committee, along with two of his guards.

In the Anbar provincial capital of Ramadi, west of Baghdad, gunmen attacked a police station, wounding one policeman, while one attacker was killed and another wounded.

Attacks elsewhere in the province killed an anti-Qaeda militiaman, a soldier and a police officer.

And a roadside bomb killed two people and wounded five in Madain, south of Baghdad.

Iraq has faced years of attacks by militants, but analysts say a fresh upsurge of violence has been fuelled by discontent among members of its Sunni Arab minority, which the Shiite-led government has failed to address.

With the latest attacks, more than 600 people have been killed in violence so far this month and over 2,800 since the beginning of the year, according to AFP figures based on security and medical sources.

Iraq: seven months of unrest and political crisis
Baghdad (AFP) July 22, 2013 - Iraq has seen an upturn in deadly sectarian violence and protests since late last year:

--2012--

- December 23: The start of major demonstrations in several provinces demanding the ouster of Prime Minister Nuri al-Maliki, a Shiite accused by opponents of monopolising power and sidelining Sunnis.

Demonstrators are demanding the liberation of prisoners and a reform of anti-terrorism laws. The action follows the arrest on terrorism charges of nine guards of Finance Minister Rafa al-Essawi, a Sunni and member of the Sunni-backed Iraqiya bloc.

--2013--

- January 16: A wave of attacks across the country leaves 49 dead and 240 injured, notably in two cities in the north at the heart of a bitter dispute between the central government and the autonomous region of Kurdistan.

- February 8: A spate of car bombs in Shiite areas kill at least 33 people, as tens of thousands of Sunni demonstrators demand the ouster of the prime minister. Attacks spiral, leaving more than 100 dead in one week.

- February 28: The government says it has freed 4,000 prisoners since the beginning of 2013, in an apparent bid to placate protesters in Sunni areas of the country.

- March 19: A wave of attacks and explosions, mainly in Shiite neighbourhoods in and around Baghdad, kill 56 people and injure more than 220.

- April 15: Dozens of attacks across Iraq, including a brazen car bombing on the way to Baghdad airport, kill 50 people.

- April 23: The beginning of a new wave of clashes which leave more than 240 dead in a week. The violence breaks out when security forces enter an area where Sunni demonstrations have been held since January near Hawijah, west of Kirkuk province's eponymous capital. Revenge attacks ensue on Iraqi forces.

- May 17: Bombs targeting Sunnis, including two near a mosque and one at a funeral procession, kill 67 people, after dozens died in two days of attacks on Shiites.

- May 27: Attacks in the Baghdad area and northern Iraq, mainly targeting Shiite areas, kill 58 people.

- June 10: A wave of violence, mostly aimed at Sunni security forces, kill at least 73 people.

- July 2: A wave of attacks, mostly targeting Shiite Muslims, including a spate of market bombings, kill 57.

- July 16: A UN envoy says that nearly 3,000 people have been killed in Iraq in four months and that the country risks stumbling onto a "dangerous path" to disarray.

- July 20: A wave of bombings kill more than 60 people in Baghdad province.

- July 22: Militants attack two Iraqi prisons, freeing at least 500 inmates in assaults that cost more than 40 lives, officials say.