RAIPUR: Indian Maoists killed at least 24 policemen, including a senior officer, in an ambush Sunday in the eastern state of Chhattisgarh, officials said.

The attack took place in Rajnandangaon district, 90 kilometres (56 miles) from the state capital Raipur, the deputy inspector general of police in charge of operations against the left-wing rebels told AFP.

The guerrillas shot dead two policemen on patrol in the area and then ambushed the security team that was sent to investigate the incident, Pawan Dev said.

"We have information now of 24 policemen being killed in the attack," he added. "The dead include superintendent of police V.K. Choubey."

Meanwhile, a Press Trust of India report said New Delhi was sending 600 paramilitary personnel to Chhattisgarh to start combing operations for the rebels responsible.

Sunday's attack comes a month after 11 special police personnel were killed in a landmine blast triggered by Maoists in Chhattisgarh, where the left-wing rebels are based.

In April the rebels took more than 300 passengers hostage in an audacious attack in the neighbouring state of Jharkhand.

The authorities have been criticised for the apparent ease and confidence with which the rebels are allowed to operate.

India's Maoists say they are fighting for the rights of neglected tribal people and landless farmers. They are now active in more than half of the country's 29 states -- particularly in the east, the poorest part of India.

Estimates of their numbers nationwide range between 10,000 and 20,000, but little is known about their shadowy leadership, which does not court the media and seldom issues statements.

Indian Prime Minister Manmohan Singh in 2006 described the Maoists -- known in India as 'Naxalites' -- as a "virus" and ranked them along with Islamic militants as a serious threat to the country's internal security.

In a statement to parliament last week, junior home minister Ajay Maken said at least 455 people had been killed in Maoist-triggered violence since January this year with Chhattisgarh alone accounting for 148 deaths.

New Delhi last month slapped a formal ban on the Maoists, officially designating the group as a terrorist organisation.

Sunday's attack comes as police in eastern West Bengal state said paramilitary troops were still struggling to retake hundreds of villages in a 1,000 square kilometre (390 square mile) area under Maoist control -- weeks after launching the security operation.