BAGHDAD (AP) -- The U.N. and several aid organizations said Tuesday that an estimated 750,000 civilians are still living under Islamic State rule in the western part of Mosul, the next target of a U.S.-backed Iraqi offensive launched three months ago.

Lise Grande, the U.N. Humanitarian Coordinator for Iraq, said the cost of food and basic goods is soaring, water and electricity are intermittent and that some residents are forced to burn furniture to keep warm.

Iraqi and Kurdish forces launched a massive operation in October to retake Mosul, which fell to IS in the summer of 2014. They have driven the militants from nearly all of the neighborhoods east of the Tigris River, which runs through the heart of the city.

"We hope that everything is done to protect the hundreds of thousands of people who are across the river in the west,'' Grande said in a statement.

"We know that they are at extreme risk and we fear for their lives.''

The statement, which was co-signed by 20 international and local aid groups, called on warring parties "to uphold their obligations under international humanitarian law to protect civilians and ensure they have access to life-saving assistance.''

Mosul is the IS group's last major urban bastion in Iraq. The extremists still control large areas in neighboring Syria.

Iraqi forces announced the liberation of eastern Mosul earlier this month.

But on Tuesday, the spokesman of the Joint Operation Command, Brig. Gen. Yahya Rasool, said fighting was still underway in the northeastern district of Rashidiya.