"Please don't get used by the Maoists... Please move away... We don't want a bloodbath"
Ardhendu Sen, West Bengal interior minister
Ardhendu Sen, the state's interior minister, said soldiers had gained a foothold in Lalgarh, but that clearing the whole area under rebel control - comprising more than 1,000 sq km - would take time.
The advance on Lalgarh was slow as the security forces had been fired on overnight, Praveen Kumar, a senior West Bengal police officer, said.
"Our men had to progress through a heavily mined forest," he said. "Bridges and culverts bombed by Maoist rebels left the roads impassable for four-wheeled vehicles."
Earlier this week, the rebels drove out the local police after deadly clashes.
The state government subsequently called in more than 1,800 paramilitary troops to retake the area.
On Thursday, hundreds of police charged and fired tear gas shells at a crowd of almost 3,000 in Pirakata, on the outskirts of Lalgarh.
Police said at least 10 party workers from the state's ruling Communist Party of India-Marxist (CPM) had been killed by recent violence and that security camps and party offices had also been burnt down.
The authorities have appealed to villagers to co-operate.
"Please don't get used by the Maoists. Please move away. We don't want a bloodbath," Sen said.
|Maoist-linked violence has killed 6,000 people in India over the past 20 years [AFP]
The Maoists had earlier claimed Lalgarh as their first "liberated" zone in West Bengal.
Lalgarh encompasses vast areas of the forests of West Midnapur, Purulia and Bankura districts of West Bengal and adjoins parts of the states of Jharkhand and Orissa.
Violence in Lalgarh began last November after Buddhadeb Bhattacharya, the state's chief minister, survived a land mine blast blamed on the rebels.
Protests were launched when a number of locals were arrested on suspicion of attempting to assassinate Bhattacharya.
The rebels, also known as Naxalites after Naxalbari, a village in West Bengal where the movement originated in 1967, say they are inspired by Mao Zedong, China's revolutionary leader.
The Naxalites have fought for several decades across India, demanding land and jobs for the poor. They have urged the government not to try to retake the Lalgarh region, warning that local support was on the side of the rebels.
Maoist-linked violence has killed 6,000 people in India over the past 20 years.