BAGHDAD (Reuters) - Islamic State insurgents killed at least 17 Iraqi soldiers with suicide truck bombs on Thursday in a major attack on government forces that recaptured the western city of Ramadi in December, military officials said.

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The jihadist group also killed two policemen and wounded eight others in two suicide bombings in Abu Ghraib outside Baghdad, a day after killing at least 80 people in bombings at an outdoor market and two checkpoints inside the capital.

The attacks near Ramadi dealt one of the heaviest blows to the army since it drove Islamic State out of the western city five months ago.

An army colonel told Reuters that militants killed at least 17 soldiers with suicide truck bombs in Jarayshi, 10 km (6 miles) north of Ramadi. They also surrounded an army regiment, seized a bridge and cut a key supply route linking Ramadi to the Thirthar district further north, army sources said.

Air strikes by a U.S.-led coalition later allowed government forces to regain control of the supply route. But despite army reinforcements, the militants had dug into northern residential areas by nightfall and were lobbing mortars at government positions across the Euphrates river.

An officer said the Islamic State attack appeared designed to delay an expected army offensive that would have completely severed militant supply routes to Falluja on the western approaches to Baghdad, which Iraqi forces have ringed for more than six months.

As Islamic State has been pushed out of key towns and cities it seized in 2014, it has resorted increasingly to guerrilla-style attacks in civilian areas under nominal Iraqi government control.

The toll from Wednesday’s three suicide bombings in Baghdad made it the deadliest day in Baghdad so far this year.

Police sources said Thursday’s bombers approached a police station in Abu Ghraib from two directions before detonating their explosives. Baghdad Operations Command, one of the security organs charged with protecting the capital, said a third assailant was killed on approach to the police station.

Amaq news agency, which supports Islamic State, said two militants had clashed with police at al-Zeidan station before setting off their explosives-filled vests.

Sunni Muslim militant violence against security forces and Shi’ite Muslim civilians has persisted since Baghdad became the target of almost daily bombings a decade ago following the U.S.-led invasion in 2003 that toppled Saddam Hussein.

A recent surge in bombings has heightened criticism of Prime Minister Haider al-Abadi as he grapples with a political crisis over his attempts to overhaul his cabinet to weed out corruption and mismanagement.

Lawmakers balking at ceding vested interests targeted by Abadi have failed to convene parliament since protesters loyal to powerful Shi’ite cleric Moqtada al-Sadr, a vocal advocate of dismantling Iraq’s quota-based governing system, breached the heavily-fortified Green Zone district two weeks ago and took over the assembly complex for several hours.

Sadr’s supporters took to the streets of Baghdad on Thursday to denounce the government for failing to protect them, escalating a political confrontation that could doom the ruling coalition.