The new vehicles, which were already in use, are believed to have considerably reduced pollution in Kathmandu, which was considered one of Asia's most polluted cities.

Rickshaws are a popular mode of transport in the sub-continent

Vehicular emissions account for a large part of the overall pollution problem in Kathmandu.

But environmentalists were shocked by a government decision last week to ban the registration of new battery operated auto-rickshaws.

This was in line with a policy of preventing new vehicles taking to the road to ease traffic congestion.

The government enforced the ban in the Kathmandu valley last week, citing the problem of overcrowding.

The authorities said the ban was temporary and that it might be lifted within three months after a study had been carried out on the capacity of Kathmandu's roads.

But there was widespread criticism from leading environmental groups, who said that the ban could not be justified under any pretext.

They said the vehicles were a cheap, efficient and environmentally-friendly mode of transport, and they called on the government to overturn the decision immediately.