At least 35 pilgrims have been killed after a bus plunged into an irrigation canal in southwest Nepal.

Most of the victims were from India and were due to attend an annual religious festival at Triveni tomorrow morning, according to police.

Police official Ram Dutta Joshi said ten people were rescued after the crowded bus fell into the water near the Hindu pilgrimage site of Triveni, 100km southwest of Kathmandu.

"We have drained out the canal and are looking for survivors," Mr Joshi told Reuters from Parasi, the nearest town to the crash site.

Indian officials have now arrived at the scene and are expected to help identify the other victims.