Suspected Maoist rebels have shot and killed three policemen and two private security guards in an attack on a private construction company complex in the eastern state of Bihar, one of India's poorest, police have said.

Maoists attacked base camp of the firm and tried to destroy a bridge over river Belaru on Wednesday, the Reuters news agency reported.

Around 50 armed Maoists arrived at the culvert in Goh area in the district and exploded bombs in a bid to destroy it, according to police.

Fighters also wounded seven police officers, two of them seriously, Bihar state's top police officer Abhayanand, who uses only one name, told the AP news agency on Thursday.

None of the Maoists have been reported to be injured.

Private television channel CNN-IBN also reported that security forces launched an operation to capture rebels on Thursday.

The attack took place in an area near Aurangabad, a town nearly 165km south of Patna, the state capital.

The area is a known stronghold of Maoist rebels who have been fighting in several Indian states for more than 40 years, and claim inspiration from Chinese revolutionary leader Mao Zedong.

Maoists are also said to have robbed some police arms. Twelve security personnel are also reported missing.

'Internal security challenge'

The Maoists, who say they are fighting for the rights of the poor and landless, and want to overthrow the government, have stepped up attacks in recent months.

Earlier this month, Maoist rebels attacked a police convoy in Dumka district of Jharkhand, killing at least five policemen.

In the month of May, the fighters killed three people in an attack on a passenger train in Bihar.

Also in May, Maoist rebels ambushed a convoy of Congress politicians in Chhattisgarh, killing at least 27 people.

The fighters, also known as Naxals, have fought for decades in a wide swathe of central and eastern India, including many resource-rich regions where tensions run high between poor farmers and industrial developers.

Indian Prime Minister Manmohan Singh has described the Maoist rebels as India's biggest internal security challenge.