GENEVA/BENGHAZI, Libya (Reuters) - Fighting in the Libyan city of Derna has escalated to unprecedented levels, with air raids and shelling of residential areas as well as heavy ground clashes, the United Nations humanitarian office said on Thursday.

There were severe water, food and medicine shortages, and electricity and water had been completely cut off for the city’s 125,000 residents, it said in a report.

The eastern city has been encircled since July 2017 by the Libyan National Army (LNA), whose commander Khalifa Haftar opposes the internationally recognized government based in the country’s west.

Haftar’s forces are trying to wrest the city from a coalition of local fighters and Islamists known as the Derna Mujahideen Shura Council (DMSC) or Derna Protection Forces (DPF).

Their surge over recent days overshadowed high-level talks in Paris on Tuesday that tried to chart a way out of Libya’s turmoil and set a goal of holding elections in December.

Following fighting on Wednesday, the LNA took control of most entry points to Derna from the west, LNA spokesman Abdulkarim Sabra said. The LNA has also claimed control of the city’s al-Fatayih Industrial Zone and strategic hills over the Bab Tubruk district.

Electricity supply was restored early on Thursday after maintenance to a power plant that was hit by shelling earlier in the week, according to Sabra and a Derna resident.

LNA forces have had about 20 men killed and 35 wounded since the fighting intensified in Derna earlier this month, mostly due to mines, Sabra added.

He estimated that more than 100 DMSC or DPF combatants had been killed and that another 100 had handed themselves in. The numbers could not be independently verified.

The LNA says it is targeting militants including foreign fighters with links to al Qaeda. Its critics say the LNA has branded all its opponents as “terrorists” as it tries to seize the only city in eastern Libya outside its control.

Until this month, the LNA’s campaign had been largely limited to occasional air strikes and bombardments. Since May 22, indiscriminate shelling had killed at least five civilians, including two children, the U.N. said.

“Local sources report that DPF are currently taking positions amongst civilian infrastructure in residential areas, mostly in the center of the city and reportedly in civilian clothing,” the U.N. report said, adding that civilians were being prevented from leaving the city.

The U.N. said no aid has entered the city since mid-March, apart from a delivery of kidney dialysis materials and medication earlier this week.

Neighboring Egypt, which backs the LNA, has also carried out air strikes in Derna against what it said were training camps sending militants into Egypt to carry out attacks.

Separately, an LNA battalion said it had repelled an attack early on Thursday against its positions at Tamanhent air base in Libya’s central desert. It has controlled the base since May last year.