India's government is warning of possible violent strikes by radical leftist insurgents. The alert comes as paramilitary forces conduct the most concerted effort in years to repel Maoists who control large swathes of eastern forests.

Policemen take position during an encounter with Maoist rebels at Bhimpur, in west Midnapore, India, 19 Jun 2009

Maoist insurgents have called for a two-day protest in an eastern swath of India where they have considerable influence. 

The Home Ministry is warning the general strike, Monday and Tuesday, may be accompanied by attacks against security forces.

Additional Home Secretary D.R.S. Chaudhary told a news conference Sunday authorities and citizens need to be vigilant, especially in five eastern states.

"There are intelligence inputs that CPI [Communist Party of India] Maoists may indulge in demonstrative acts of violence by targeting security forces and economic infrastructure, such as trains, buses, railway stations, bus stations and other places where people are likely to gather," said Chaudhary.

The alert focuses on five states: Bihar, Chhattisgarh, Jharkhand, Orissa and West Bengal.

Security experts say armed Maoists, also known as Naxalites, number about 20,000 and control about one-fifth of India's forests.

The warning comes as para-military forces re-captured a police station in Lalgarh in West Bengal. The insurgents claimed to have liberated the town from state control.

That prompted the central government to dispatch border security and police reserve forces to the area. They are backed by a new squad, known as Combat Battalion for Resolute Action - or COBRA - formed specifically to take on Naxalites.

Meanwhile, police say at least eleven members of the Central Reserve Police Force died when their vehicle hit a landmine in an area of Chhattisgarh, where Maoists are active. About a dozen more officers were injured when the truck exploded and flipped over.

Police say the survivors exchanged gunfire with the insurgents, killing seven of the heavily armed guerrillas in the encounter Saturday night.

The low-level rural insurgency has frustrated Indian authorities for decades. Recently, Prime Minister Manmohan Singh labeled it the biggest internal security threat India is facing.

The ultra-left movement claims it is a grassroots rebellion fighting against oppression, exploitation and corruption.