Rebels control a chain of mountain-top towns on the western front of Libya’s two-month-old conflict, linked by a single road running some 200 km from the Tunisian border to within 150 km of the capital, Tripoli.

But Qaddafi troops hold the desert plains below, and the road is exposed at several low sections — a concern for aid agencies trying to enter opposition-held territory in defiance of the government.

Most are working through low-key local partners, limiting their capacity and reach.

In Zintan, the last opposition-held town in the chain, there are queues outside the only bakery still working and almost no fruit or vegetables on sale.

Onions and potatoes can sometimes be bought from the boot of a car. The town is surrounded at a distance of some 15-30 km on three sides by Qaddafi soldiers in the desert.

Food aid is getting in, but it is mainly milk, dried pasta, rice and tinned food lacking nutrients. Almost all shops are shuttered and gas stations ran dry weeks ago.

Fuel is bought off the back of a trailer in the town center for 2.50 dinars ($2.00) per liter, more than 15 times the pre-war price. There is particular concern for the remote mountain town of Yefran, east of Zintan and outside opposition-held territory.

A Yefran resident who moved to Zintan at the outbreak of fighting said many women and children had already fled, but the men who stayed are surrounded on all sides by Qaddafi forces, choking supplies of food and medicine.

The man, who declined to be named, told Reuters he had been part of a opposition operation last month that punctured Qaddafi lines to briefly reach the town and bring several people out, but that communication had since been lost.

The World Food Program (WFP) said on Thursday it was increasingly concerned about access to food for people trapped by fighting in the region.

“We have not yet been able to reach the areas most affected by the fighting around Yefrin and Zintan in the Western Mountains,” WFP executive director Josette Sheeran said. The supply route is now facing serious challenges due to insecurity in many of the areas, in addition to severe fuel shortages. More than 40,000 people have left the region for Tunisia, leaving a number of towns populated almost entirely by men. Refugees have reported male relatives disappearing from towns in the plains controlled by government troops.

Fighting has intensified over the past several weeks around Zintan, which has also come under often indiscriminate artillery attack by pro-Qaddafi forces.

Government officials in Tripoli deny attacking civilians, and say the fighters are armed criminals and Al-Qaeda militants. It says most Libyans support Qaddafi, in power for four decades.

On the heaviest battle days, the hospital in Zintan, with only one dedicated operating theater, struggles to cope with the numbers and the severity of the wounds from gunshots and shrapnel.

Another two makeshift operating theaters have recently been opened, and medical supplies have so far managed to make it up the road from the Tunisian border. “This hospital was never doing any major surgery before. The whole system was based on referral to Tripoli, and now thats not possible,” Dr Morten Rostrup of Medecins Sans Frontieres said.

Last weekend, the hospital treated around 50 fighters wounded, some critically, in clashes east of Zintan, despite having capacity for a maximum of 20.

A doctor who gave his name as Tahar said the hospital had filled up in less than two hours.

“We are severely depleted,” he said.

The worst cases are transferred by ambulance across the border to Tunisia, a journey of several hours.

The hospital is also coping with a lack of trained staff. Many medical workers in Libya before the war were brought in from abroad from countries such as Bangladesh and Ukraine. Almost all left Zintan when the fighting started.

The border crossing has changed hands several times, and is currently controlled by the fighterss. There are fears that if Qaddafi forces manage to take it back, they will choke off supplies to the entire Western Mountain region. “We are totally dependent on supplies across the border,” Rostrup said.