At least 37 people have been killed after a packed passenger bus ran over a suspected rebel landmine in southern Nepal, the authorities say.

Another 70 people were injured in the blast in Chitwan district, in what the army says was a Maoist ambush.

Reports say the vehicle and many of those inside were blown to pieces.

Correspondents say, if confirmed, it is one of the biggest civilian death tolls since the Maoist rebels began their fight for a republic in 1996.

Abuses

Eight ambulances have gone to the scene of the disaster.

A local official says a helicopter is also being used in the rescue effort.

There has been no word yet from the rebels.

The BBC's Charles Haviland in Kathmandu says they are likely to be blamed for the killings, although they have tended to avoid attacks of such an apparently indiscriminate nature.

About 12,000 people, many of them civilians, have died in Nepal's conflict, the army says.

Human rights groups accuse both rebels and the security forces of abuses.

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Nepalese soldiers. (AFP)