About 70 policemen have gone missing in the central Indian state of Chhattisgarh following an ambush by suspected Maoist rebels.

The ambush by about 200 rebels on Wednesday could be one of the worst attacks this year in a spiralling insurgency.

"The policemen were ambushed in a forest by Maoists as they were returning to a police station," Rabndra Nath Chowdury, a journalist with the Deccan Chronicle newspaper told Al Jazeera.

Maoists waged a fierce gun battle with law enforcement officers in the dense forest, and communication was difficult because of heavy rain, the police said.

T J Longkumer, the inspector general of police, estimated that 70 policemen were  missing. "We have not been able to establish contact," he told Reuters.

Rebel stronghold

The brazen ambush highlights the strong rebel presence in significant portions of India, especially in poor rural regions left out of India's economic boom.

In a separate attack in eastern Jharkhand state on Tuesday, rebels killed five people, police said. It was not immediately clear why the Maoists killed them.

Security forces launched a counter-offensive against Maoists earlier this year but recent attacks raise questions over how well prepared security forces are to tackle the insurgency.

In April, a similar ambush by Maoists killed 75 policemen and a month later a bus bombing killed 35 people, including security forces.

Both attacks occurred in the mineral-rich but largely poor Chhattisgarh state.

Rebels claim to be fighting for the right of poor peasants and landless workers and aim to topple the Indian state by 2050.

They operate from jungle bases and launch hit and run attacks on police, transportation networks and government buildings in east, central and southern India, where they control large territories.

Thousands have been killed since the insurgency started in the late 1960s and the Indian government has said that Maoist fighters represent the country's most dangerous internal security threat.