KATHMANDU -- The death toll from a strong, shallow earthquake in western Nepal has risen to 128 as the rescue operation is going on, government officials said on Saturday.

The 6.4-magnitude quake hit Jajarkot and Rukum West districts in western Nepal at 23:47 local time on Friday night (1802 GMT), killing 128 people in the districts and wounding 140 others, Nepal Police spokesman Kuber Kadayat told Xinhua.

It is difficult for the rescue teams to reach some places as bridges were damaged, and roads were blocked by landslides triggered by the quake, he said.

The depth of the earthquake is between 10 to 15 km, and an additional four aftershocks above magnitude 4.0 have been recorded by Saturday morning, according to Lok Bijay Adhikari from Nepal's National Earthquake Monitoring and Research Center.

"The aftershocks continue," he added.

The Nepali government is focusing on the rescue and treatment of the injured after the earthquake.

"The rescue and treatment of the injured is the first priority," Home Ministry spokesman Narayan Prasad Bhattarai told Xinhua.

Nepali Prime Minister Pushpa Kamal Dahal went to the affected area Saturday morning along with health workers, and helicopters were being mobilized for the rescue operation, he said.

"We have not yet taken details about houses and other infrastructure damaged as the focus is to rescue," said Bhattarai. "So far, there is no report of casualties from other districts."

In October, three quakes above magnitude 4.0 jolted the Dhading district in central Nepal, with one measuring 6.1-magnitude.

A 7.8-magnitude earthquake in 2015 killed some 9,000 people and damaged more than half a million houses in the mountainous country.