After foiling resistance by Maoist-backed tribals, security forces on Friday resumed their push cautiously towards Lalgarh, a stronghold of the ultras, sweeping the roads for mines as the agitators blew up a bridge to stall their movement.

The forces moved out from Pirakata where they had halted for the night and resumed the march towards Lalgarh, 26 km from here, in a pincer movement from Pirrakuli and Sarenda in adjacent Bankura district, a senior police officer said.

They used mine detectors to sweep the roads and forests before driving ahead in heavy vehicles from Pirrakuli, 10 km from here.

An IAF helicopter made a sortie over Lalgarh, where Maoist leaders, including a key functionary Kisanji, were believed to be holed up, dropping leaflets asking the people not to allow themselves to be used as human shields.

The tribals under the People's Committee Against Police Atrocities blocked all the roads leading to Lalgarh which has come under their control with the police having withdrawn from camps earlier fearing capture of their weapons.

Roads at Dahijuri and Dherua were dug up and trees felled to obstruct the advance by armed police and Central security forces, while a bridge over a river at Binpur was blown up, the police official said.

The security forces planned to set up base camps at Goaltore, Salboni and Jhargram, besides in Pirakata, he said.

The police official also said that CRPF personnel were being posted on cleared roads.

A contingent of the Command Battalions for Resolute Action (CoBRA), a specialised anti-naxal force, was on standby.

A team from the Kolkata police led by Joint Commissioner of Police Ranbir Kumar reached Jhargram to oversee law and order there as the people fleeing Lalgarh would head for the town.

Another helicopter has been sought for evacuating injured security personnel to hospitals.

Meanwhile, Kisanji warned the police not to enter Lalgarh, which was echoed by PCAPA leader Chhatradhar Mahto. A police official said Kisanji and Mahato's comments indicated either the agitators were scared or they had laid a trap for the security forces.

IGP (Western Range) Kuldip Singh told PTI, "The operation will continue till all Maoists are cleared from Lalgarh."

The IG (Western Range) said, "So far, five companies of CRPF, two companies of State Armed Police (SAP) and one company of BSF have been deployed to clear the road to Lalgarh."

A senior police officer said, "We want the least bloodshed since the tribals are using human shields. We will use lathis, teargas and rubber bullets for dispersing mobs."

"The Maoists are keeping women and children in front, while they position themselves at the rear of the human shields," he said.

"Our primary target is to cut off the Maoists from the people," he said.

"Though the Maoists are armed with AK 47 and INSAS rifles, we hope to immobilise them," said the officer.

Close surveillance was also being made on the Jharkhand border from where the Maoists were suspected to be entering Lalgarh, he said.