Tens of thousands of Iraqi troops and Kurdish Peshmerga forces are focusing on districts along the Tigris River.

Iraqi troops have resumed a coordinated offensive towards Mosul, the last major city held by ISIL in Iraq, targeting the eastern bank of the Tigris river that divides the city, military officials said.

Army units had paused their advance last week after they made ground quicker than forces on other fronts, to allow them to close the gap and get nearer to the city.

“The operation to liberate the left bank of Mosul has started,” said a military statement on Monday, referring to the eastern bank of the river that flows from north to south.

Another statement said five villages were retaken from the Islamic State of Iraq and the Levant (ISIL) group north of Mosul, where Peshmerga fighters are also being deployed.

Al Jazeera’s Stefanie Dekker, reporting from Erbil, said that it is the closest position to any of the fronts surrounding the city, adding that it is “not an easy fight”.

READ MORE: Iraq – Thousands displaced as battle for Mosul rages on

“This offensive is led by Iraq’s special forces that will go into Mosul. They are very well trained but we don’t expect to see them going into the city anytime soon,” she said.

“They are facing fierce resistance, it’s been very difficult as we have been told. Fighters are continuing suicide bombings, car bombs and artilleries. However, this is an effective attempt to put more pressure on ISIL as the fight is ongoing.”

Iraqi security forces and Kurdish Peshmerga fighters started the offensive on October 17, with air and ground support from the US-led coalition against ISIL, also known as ISIS.

Pro-Iranian Iraqi Shia militias joined the fighting on Saturday, aiming to cut the route between Mosul and Raqqa, ISIL’s main stronghold in Syria.

READ MORE: Shia militias open new front in battle for Mosul

The battle for Mosul, still home to 1.5 million residents, is shaping up to be one of the toughest in a decade of turmoil following the US-led invasion that toppled Saddam Hussein in 2003.

ISIL members have been fighting off the two-week offensive with suicide car bombs, snipers and mortar fire.

Worst-case United Nations forecasts see up to 1 million people being uprooted by the fighting, which UN aid agencies said had so far forced about 17,500 people to flee, a figure that excludes those taken into Mosul by the retreating fighters.