A fuel crisis in Nepal has disrupted aid agencies' efforts to send essential items like blankets and clothing to earthquake survivors in remote mountainous areas before winter sets in, aid workers say.

Protests at the Indian border over Nepal's new constitution, which began in September, have prevented tankers from taking petroleum into the landlocked Himalayan nation, forcing Kathmandu to ration fuel and import supplies from China.

Aid groups supporting people hit by twin earthquakes in April and May say the mile-long queues for fuel and the lack of cooking gas have affected hundreds of thousands of people in the impoverished nation, including quake survivors.

"Hospitals have run out of essential drugs and supplies, vital social services have been disrupted and aid agencies such as Oxfam have not been able to secure fuel to deliver relief items to prepare people for the winter in earthquake affected districts," said Cecilia Keizer, head of Oxfam in Nepal.

"If the situation continues, Oxfam's humanitarian program will come to a complete standstill within two weeks," Ms Keizer said in a statement.

Oxfam, which was planning to deliver thermal mats, blankets and hot water bottles to people in rural areas, said it had already had to reduce its program.

More than 40 people have died in violent protests at border posts with India, where some southerners have blocked fuel imports, saying their Tarai Madhes region has been carved up in a way that gives them no say in running the nation of 28 million.

Many Nepalese accuse India of supporting the protesters.

New Delhi denies the charges, but has said it cannot allow trucks to enter Nepal while conditions are unsafe.

Max Santner, the head of the International Federation of Red Cross and Red Crescent Societies (IFRC) in Nepal, said the IFRC has had to change the type of relief it was providing to around 48,000 quake survivors.

Sorry, this video has expired No end in sight for Nepal's crippling fuel crisis ( South Asia correspondent James Bennett )

"The shortages of fuel are definitely hindering our operations," he said.

"Instead of providing blankets and clothing for the winter, we are going to distribute cash vouchers as we don't have the fuel to take up trucks filled with aid.

"We hope that people will be able to buy winter items where they are, but we are not sure on availability."

Aid workers said the shortages of fuel and basic goods had not reached emergency levels, but they were trying to save fuel.

"We have reduced non-essential travel, we are doing more car pooling and increasing the number of staff travelling in one vehicle," said Jeff Franklin from Save the Children in Nepal.

"We have also applied for a fuel-import licence, increased the amount of funds we are appealing for to take into consideration the higher costs of fuel and are tapping into fuel provisions offered by the UN."

Reuters