Agence France-Presse .

Bhubaneswar Maoist rebels in eastern India have shot dead 13 police and a civilian in the worst attack by the leftist insurgents in months, officials said Saturday. Hundreds of rebels, including women fighters, attacked two police stations in Orissa state late Friday and looted weapons before escaping, witnesses said. Fifteen people, most of them police, were also wounded.

 'The security personnel were simply outnumbered,' admitted the state's chief minister, Naveen Patnaik, who also appealed for federal help. Orissa is one of India's poorest states and part of an eastern swathe of the country where the Maoists, who say they are fighting for the rights of neglected tribal people and landless farmers, appear to be gaining ground.

The attack also took place in the mineral-rich coastal state's Nayagarh district, a mere 100 kilometres west of the state capital Bhubaneswar. 'The attack was sudden and in the middle of the night. They killed 13 policemen and a civilian,' superintendent of police Rajesh Kumar said. The attack took the authorities by surprise, as the Maoists had previously not been active in Nayagarh – although similar attacks elsewhere in Orissa have occurred twice in the past three years.

'They attacked the Nayagarh district police station and the nearby Daspalla police station,' Kumar said, adding that the guerrillas had also set one of the police stations on fire, fired at a police training school and raided an armoury. The official said the police were still trying to establish how many weapons were stolen. Indian press reports said fighting was continuing with the escaping rebels in nearby districts, with 600 extra police called in. 'The Nayagarh-Daspalla sector will have more (police) force to combat the Maoist menace,' said director general of police Gopal Nanda.

The Maoist insurgency, which grew out of a peasant uprising in 1967, has hit half of India's 29 states and is centred in a heavily forested region in central Chhattisgarh state, which borders Orissa. Last year, 834 people were killed in Maoist-related violence nationwide. In December, the Indian prime minister, Manmohan Singh, warned that the shadowy Maoist guerrillas – known in the country as 'Naxalites' – were stepping up their insurgency in vast areas left out of India's economic boom.

The premier has described the ultra-leftist revolutionaries as the biggest single threat to internal security, and has called for the formation of a dedicated security force to tackle what he said was a 'virus.' The latest violence came a day after the federal government announced more security forces and armoured vehicles to combat the guerrillas in Chhattisgarh.