Suspected Maoist rebels set off two bombs in the eastern Indian state of Chhattisgarh yesterday, killing 13 people, most of them paramilitary soldiers and officials charged with holding elections in the region.

The attacks, half an hour apart, were the most serious since voting to elect a new federal government began last week in a six-week process to allow security forces to move across the country.

The first explosion took place in a bus in Bijapur carrying election officials who were on their way back after completing the vote. Seven people were killed.

A second bomb hit an ambulance in the thickly forested Bastar region killing five members of the Central Reserve Police Force and their driver, said R.K.Vij, the head of anti-Maoist operations.

It was not clear why the soldiers were travelling in the ambulance, but in the past government officials are known to be have used such vehicles to avoid attacks by the Maoists.