Police in the southern Indian state of Andhra Pradesh say at least 14 people have been killed by suspected leftist guerrillas who set off a landmine under a bus.

Forty people were on the bus and many of the survivors are said to be critically injured.

The attack took place in a village in Warangal district, some 200 kilometres (124 miles) north of the state capital Hyderabad.

A local police official, Gautam Swanga, blamed the blast on the Maoist guerrillas of the Naxalite People's War Group, which has been fighting a campaign in five southern states.

The Press Trust of India news agency said it appeared that the rebels detonated the device by remote control.

Deputy Swanga said that after the bus was destroyed, the attackers opened fire on the burning wreckage, apparently thinking it was a police transport.

He said no policemen were on the bus, adding that the attackers had committed a "ghastly mistake".

The death toll is expected to rise since the attack took place in an area where there were no medical facilities, the Associated Press news agency reported.

Forest hideout

The latest attack comes after police killed five rebels, including two women, in the area on Sunday and security forces were continuing to patrol the district.

The blast is reported to have take place in a forest where rebels have been hiding out with the support of local villagers.

But Deputy Swanga said the bus attack was likely to turn public opinion away from the rebels.

"They think they are secure in their forest, but they won't be any more," he said.

More than 6,000 people have been killed in fighting since the Naxalite People's War Group began its campaign against police, political officials and landowners more than 20 years ago.