Many dead in India bus blast

At least 20 people, including policemen, were killed when Maoist rebels detonated a landmine under a bus in central India, the second major attack in as many months.

Local reports say the death toll could be as high as 35. The attack in the mineral-rich state of Chhattisgarh was the worst since a strike by Maoists in the same region in April which killed at least 75 policemen.

Home Minister Palaniappan Chidambaram said it may trigger a change in the government's strategy against the Maoists in some states.The chief ministers of several states racked by Maoist violence had asked for military support, he said.

The attack occurred in Dantewada district of Chhattisgarh, said to be the worst hit by four decades of an insurgency that has killed thousands of people and has been described by the government as India's gravest internal security threat.

The rebels have stepped up attacks in response to a government offensive. Police say recent attacks are an act of desperation, but the strikes have also raised questions about how well prepared security forces are to tackle the Maoists.

The Maoists control large but poor areas of the region and often attack railway lines and mining operations to cripple economic activity, such as the transportation of coal to power and steel companies.