Iraqi forces pushed Islamic State fighters back further in Mosul on Tuesday in a renewed effort to seize the northern city and deal a decisive blow to the militant group, though progress was slow in some districts, the army said.

Iraqi forces and their allies have captured villages and towns surrounding Mosul and seized at least two-thirds of its eastern districts, military officials say, reaching the eastern bank of the Tigris river for the first time on Sunday.

The government had initially hoped to retake Mosul by the end of 2016 but three months into the U.S.-backed campaign, the militants control the territory to the west of the Tigris that bisects the city from north to south.

Iraqi Prime Minister Haider al-Abadi said in December it would now take another three months to drive the militants out of Mosul, the largest city under Islamic State control in Iraq or Syria.

Civilians wounded in the fighting streamed into nearby hospitals and Iraqi forces blamed Islamic State for shooting at fleeing residents and shelling populated areas after losing control of them.

United Nations humanitarian spokesman Jens Laerke said nearly 700 people had been taken to hospitals in Kurdish-controlled areas outside Mosul in the last week and more than 817 had required hospital treatment a week earlier.

"Trauma casualties remain extremely high, particularly near frontlines," he told reporters in Geneva.

The World Health Organization (WHO) said about 50 wounded patients a day had come into emergency wards in Erbil over the past two weeks, up from 32 a day previously.

BRIDGES BLOWN

Recapturing Mosul after more than two years of Islamic State rule would probably spell the end of the Iraqi side of the group's self-declared caliphate, which spans Iraq and Syria.

But advances inside Mosul slowed in November and December as troops engaged in tough urban warfare with the jihadists, who are thought to number several thousand in the city.

The militants fought back with suicide car bombs and snipers hidden among the civilian population. They have also recently blown up sections of two bridges crossing the Tigris to try to slow the Iraqi advance, military officials say.

Abadi said on Tuesday the destruction of the bridges would not stop Iraqi forces from "liberating ... the people of Mosul".

One resident reached by phone in a recently recaptured district of Mosul said shells had continued to fall near his home, forcing him to move his family to another neighborhood.

"In the 10 days since we were liberated, the bombs haven't stopped. Shells fall every day near the house and we've seen civilians killed and wounded several times," he said, without giving his name.

Another resident said he had heard an Islamic State radio broadcast urging fighters to fire at areas were the civilians remained once the Iraqi army had moved in.

OIL EXPORTS

The number of people driven out of their homes by fighting spiked around the beginning of the new push by Iraqi forces, but has since returned to previous levels, the U.N.'s Laerke said.

Since the offensive started in October, some 135,000 people have been displaced, he said, adding that a non-governmental organization had opened a field hospital east of Mosul to take the strain off hospitals in Erbil, some 60 km (40 miles) away.

In a sign Baghdad is keen to revive parts of its economy hit by Islamic State's expansion more than two years ago, the oil ministry said this week it might resume exports via a pipeline to Turkey through Nineveh province, where Mosul is located.

Relations with Ankara may have to improve first, however.

Abadi said relations "cannot move forward one step" without the withdrawal of Turkish troops from Bashiqa camp near Mosul.

Turkey's military presence in northern Iraq, where its forces have trained Sunni and Kurdish fighters, has been a point of friction between the two regional powers since well before the Mosul campaign began.

Iraq's oil ministry also invited an Angolan oil company to start work at two oil fields close to Mosul, which Islamic State withdrew from months ago, setting oil wells alight as they left.