In the worst road accident in Nepal this year, at least 25 people were killed when a bus fell off the highway and plunged into a river in western Nepal Thursday with eyewitnesses fearing the toll could go up.

The accident occurred around 7 a.m. in a village called Kittu as the passenger bus run by the Kakre Vihar Yatayat, a private transport company, was heading towards Surkhet district from Dailekh, police said.

It fell off the Kalikot-Surkhet highway into the swirling Karnali river below, killing 18 people on the spot.

Of the 12 seriously injured passengers rescued by villagers, two died while being put in a helicopter that had been rushed to the spot to airlift them to the nearest hospital in Nepalgunj town, said Karna Bahadur KC, a villager who had gone to take part in the rescue operations.

Only 12 of the dead passengers had been identified till afternoon. They included a husband and wife pair and a mother and daughter duo.

Karna Bahadur said there were at least two infants among the dead.

Overcrowding could have been the reason for the accident.

The army sent a team of doctors to the area to tend to the injured.

Police said divers were still searching the waters to locate other passengers.