At least 157 people were killed in an overnight earthquake that struck a remote pocket of Nepal, officials said on Saturday, as security forces rushed to assist with rescue efforts.

The force of the 5.6-magnitude tremor jolted households awake and flattened mud houses in communities across isolated western districts of the Himalayan republic late on Friday.

"There was a very big noise when the houses came down. It felt like a big explosion," Shiva Prasad Sharma, 65, said outside the destroyed remnants of his home in Jajarkot, the district hit worst by the quake.

"I thought we were going to die," he added. "No one has anything left. There are no houses left to stay in."

Locals frantically dug through rubble in the dark to pull survivors from the wreckage of collapsed homes and buildings, as others crouched outside for safety.

The quake was felt as far away as India's capital New Delhi, nearly 500 kilometres from the epicentre.

"The toll from the quake has reached 157 – 105 in Jajarkot and 52 in Rukum," national police spokesman Kuber Kathayat said.

Another 199 were injured in the quake, he added.

Home ministry spokesman Narayan Prasad Bhattarai said the toll was unlikely to significantly increase.

"We are now in touch with all areas," he said. "It is possible some bodies might still be found under the rubble."

Security forces were deployed on foot and in helicopters to assist with search and rescue operations. (AFP)