At least 331 deaths have been reported in eastern Ukraine since last month's cease-fire deal between Russian-backed separatists and government troops, the United Nations said Wednesday.

Hostilities are persisting in the main rebel-held city of Donetsk, as well as around the towns of Debaltseve and Schastye.

Donetsk airport, the focus of much of the fighting, has no immediate tactical significance for separatist forces devoid of any air power. However, the government's hold on the facility gives it a strategic position to attack rebel positions in the city.

At least 3,660 people have been killed over six months of fighting, according to U.N. estimates. The U.N. says some deaths reported since the Sept. 5 truce agreement may include individuals killed before that date.

Donetsk city hall reported Wednesday that three civilian died overnight from shelling. There appeared to be no sign of unrest in the city throughout the morning.

U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein said in a statement that the security crisis needed to be tackled so residents of east Ukraine could reclaim their rights to education, adequate health care, housing and employment. The U.N. estimates some 5 million people are being deprived of their basic rights in east Ukraine.

"While the cease-fire is a very welcome step toward ending the fighting in eastern Ukraine, I call on all parties to genuinely respect and uphold it, and to halt the attacks on civilians and civilian infrastructure," Zeid said.

Rebels and government officials regularly blame each other for the civilian deaths.

Separatist fighters have been observed firing artillery from residential areas, eliciting hasty responses from Ukrainian troops that often miss their mark and hit houses.

The U.N. report cites the Ukrainian government as saying more than 4,500 residential buildings have been damaged or destroyed in the fighting. At least 22 settlements remain without running water, while another 93 settlements have no electricity, the report said.

Lack of proper housing is becoming particularly acute with the approach of winter, when temperatures in the region can drop below freezing for weeks on end. According to government information from mid-September, some 25,500 displaced people were living in shelters unsuited for winter residence, the U.N. said.