ISIL fighters launched ferocious counter-attacks on Saturday in territory Iraqi special forces captured in Mosul's eastern edges, highlighting the tough battle ahead as troops push into densely populated neighborhoods.

Fighters from the armed group emerged from deeper in the city to target Iraqi soldiers with mortars and suicide car bombs. They also attacked the southern edge of the Gogjali district, which Iraqi forces declared "liberated" earlier this week, pushing back some gains.

Street battles continued with both sides firing mortar rounds and automatic weapons at each other's positions, while Iraqi troops also responded with artillery.

Clashes were most intense in the al-Bakr neighborhood. Sniper duels played out from rooftops in the mostly residential areas, where the majority of buildings are two stories high.

Lieutenant-Colonel Saad Alwan, from Iraq's counter-terrorism unit, told Al Jazeera the street battles were ferocious.

"We're facing fierce resistance, they're digging trenches and using car bombs," Alwan said.

More evidence of daunting fortifications emerged on Saturday, with satellite images showing ISIL had set up defenses to bog down advancing forces, including rows of concrete barricades, earth berms, and rubble blocking key routes leading to the center of the city.

Slow southern advance

Advances towards Mosul have been slower from the south with government troops still 35km away, yet some progress has been made, Iraqi forces say. They assaulted ISIL positions in the town of Hammam al-Alil on Saturday, which lies along the Tigris river about 15km from the southernmost parts of Mosul.

Truckloads full of as many as 1,600 civilians may have been forcibly moved from Hammam al-Alil to Tal Afar earlier this week, and may be transferred onward into Syria for possible use as human shields, the office of the UN High Commissioner for Human Rights warned on Friday.

Another 150 families from the town were moved to Mosul itself, it said.

Mosul is the only major Iraqi city still held by ISIL, also known as ISIS, which seized control of the city in 2014.

Last month, Iraqi troops and special forces, Shia militias, Kurdish Peshmerga fighters, and other groups backed by US-led air raids launched a campaign to retake the city.

Meanwhile, an aid agency said on Saturday the number of displaced people had risen sharply, with more than 9,000 new arrivals in camps outside the city.

"This is the beginning of a massive exodus from Mosul city," Wolfgang Gressmann, of the Norwegian Refugee Council warned. "We must insist that civilians fleeing have genuinely safe exit routes out of the city."

The agency said at least 1.2 million people were thought to be trapped inside Mosul and some 700,000 "might soon require humanitarian assistance".

PHOTO CAPTION

Iraqi special forces soldiers drive in a desert near Mosul, Iraq October 25, 2016. REUTERS

Al-Jazeera