Iraqi forces advancing from two opposite directions in Anbar have joined up, reducing the isolation of the city of Haditha, military sources said on Monday.

A statement from Iraq's joint operations command coordinating the fight against the Islamic State group said forces retook several villages from the jihadists along the Euphrates River.

The Iraqi army's 7th division had been moving down the river from Al-Baghdadi and eventually joined up with forces from the counter-terrorism service moving up from the town of Heet.

"The road is therefore open between Heet and Haditha, via Al-Baghdadi, after an 18-month siege by the terrorists of Daesh," the statement said, using an Arabic acronym for IS.

"The siege of Haditha and Al-Baghdadi was broken after liberating the strategic highway between Baghdadi and Heet," Major General Ali Ibrahim Daboun, the army commander responsible for the area, told AFP.

However, a commander of Haditha's tribal fighters said the area of Al-Dulab, which lies in a loop of the Euphrates just east of Al-Baghdadi, was still in IS hands.

"The people are hopeful but for now nobody will take the risk of travelling on this road so long as Al-Dulab has not been retaken," Sheikh Abdullah al-Jughaifi told AFP by phone from Haditha.

Haditha, 210 kilometres (130 miles) northwest of the capital Baghdad, is the third city in the vast province of Anbar and lies near the country's second largest dam.

It has come under repeated attack since the jihadists launched their massive offensive in Iraq in June 2014, but the dominant tribes there were opposed to IS and able to hold them off.

For months, the city's main lifeline was the nearby military base of Al-Asad, which was only accessible by air.

"The engineering corps of the army continues to remove explosive devices to reopen the road for goods, oil products and food," Daboun said.

Iraqi forces, with backing from the US-led coalition that carries out daily air strikes against IS, has retaken significant ground from the jihadists in recent months.

IS still controls Fallujah city only 50 kilometres (30 miles) west of Baghdad, but it is almost completely besieged by pro-government forces.

The jihadists also hold large areas deeper in the province, including along the border with Syria.