MAOIST insurgents claiming to fight for India's rural poor killed at least 76 soldiers overnight in a series of carefully planned ambushes in the forests of eastern India, underscoring the rebels' strength despite a government offensive.

The attack by hundreds of Maoists in a rebel stronghold in Chhattisgarh state was the deadliest by the militants against government forces in their 43-year insurgency.

The rebels launched the initial attack early in the morning local time, firing on a group of soldiers as they returned to base from a two-day patrol in Chhattisgarh's Dantewada forests, SK Pillai, the federal home secretary, said in New Delhi.

More soldiers were killed when they stepped on land mines the Maoists planted throughout the ambush zone, he said.

RK Vij, the inspector general of the Chhattisgarh police, said 17 more soldiers who went to recover the bodies were killed in land mine explosions.

More than 500 guerrillas - known as Naxalites - were involved in the attacks, said Insp-Gen Vij.

He said 76 soldiers were killed and seven wounded, three critically. The government found no rebel bodies.

Indian Home Minister Palaniappan Chidambaram, the nation's top law enforcement official, said the soldiers were part of a joint operation involving state forces and paramilitary fighters.

"But something has gone very wrong. They seemed to have walked into a trap set by the Naxalites. Casualties are quite high and I am deeply shocked," he said.

Few other details were available from the isolated, thickly forested area. The rebels rarely speak to the press.

Inspired by Chinese revolutionary leader Mao Zedong, the rebels have tapped into the rural poor's growing anger at being left out of the country's economic gains and are now present in 20 of the country's 28 states.

Named after Naxalbari, the village in West Bengal state where their movement was born in 1967, they have an estimated 10,000 to 20,000 fighters.

While many are poorly armed - often going into battle with handmade weapons forged from plumbing pipes - they regularly launch bloody attacks on government forces. In February, they killed at least 24 police officers in West Bengal state in an attack on their camp.

The government dismisses Naxalite claims to speak for the country's poor, arguing they do little but wreak havoc in some of India's most impoverished regions.

"The Maoist ideology is a dead-end ideology. The killing of innocent people as well as destruction of public property, including schools, bridges, roads and culverts has really nothing to offer to people whom they claim to represent," Mr Pillai said.

The soldiers attacked overnight were part of the government's Operation Green Hunt offensive, which is aimed at flushing the militants out of their forest hide-outs.

Several experts questioned the government offensive, saying inadequately trained and poorly equipped soldiers were often sitting ducks for Maoists much more familiar with the terrain.

"It's a flawed operation," said KPS Gill, a retired senior police officer involved in operations in several insurgency-hit areas. The heat alone, he said, would weaken soldiers on long patrols.

April temperatures in the area often hit 43 degrees Celsius.

In the past few months that the Indian government has cracked down on the rebels it has also said it was ready to discuss all their demands, but only if they gave up violence. About 2000 people - including police, militants and civilians - have been killed over the past few years.

Originally published as Maoist rebels kill 76 soldiers