A bus carrying Indian tourists has crashed into a rain-swollen river in neighbouring in Nepal on Friday, killing 27 people and injuring 16.

Shailendra Thapa, a spokesperson for the Himalayan nation's armed police, said that all 41 passengers and two crew were Indian. 

They were headed to capital Kathmandu from the tourist city of Pokhara when the accident occurred, he added.

Rescue workers recovered 27 bodies from the wreckage and flew the 16 injured to the capital Kathmandu for treatment, according to Mr Thapa.

Police and army teams climbed down long metal ladders to reach the river, using ropes to pull out the injured and dead.

Exhausted women and children lay amid debris scattered on the banks of the fast-flowing river as rescuers hauled a nearly fainting child out of danger.

The bus veered off Prithvi Highway and rolled toward a fast-flowing river.

Its roof was ripped open before stopping on the rocky bank just shy of the Marsyangdi's rushing, murky water.

The Indian Embassy in Kathmandu said the bus fell about 150 metres from the highway, and they were coordinating with local authorities undertaking relief and rescue operations.

Police and army rescuers helped pull people from the wreckage near Abukhaireni, a town about 120 kilometres west of the capital, Kathmandu.

India's neighbouring state of Uttar Pradesh, where passengers boarded the bus, is sending an official to coordinate rescue efforts, news agency ANI said.

In July, two buses were swept by landslides not too far from Friday's accident site.

Of the 65 people on board those two buses, only three survived and only about half the bodies were recovered. 

The wreckage of those buses have not been found yet but authorities have continued to search.

Bus accidents in Nepal are mostly due to poorly maintained roads and vehicles and much of the country is covered by mountains with narrow roads.

AP