A bus packed with villagers went off a hilly road in east Nepal on Monday, killing 33 people and injuring 28, officials said.

The bus was carrying villagers from Kathmandu to Kavre, 40 km (25 miles) east of the capital when it veered off the Arniko highway and fell 200 metres (656 feet) down steep slopes.

"A military helicopter plucked the injured to hospitals in Kathmandu," Home Ministry official Chiranjivi Nepal told Reuters. Broken parts of the bus and belongings of the passengers were scattered at the crash site, police said.

Relatives of the victims crowded outside the National Trauma Centre in the heart of Kathmandu where the injured were taken, witnesses said.

The poor condition of roads and ill-maintained vehicles contribute to frequent road accidents in mostly mountainous Nepal. Police said the cause of the latest crash was unclear.