A landmine explosion, thought to be the work of Maoist rebels, has killed at least 15 Indian policemen, according to officials.

The explosion occurred on Tuesday in the western Indian state of Maharashtra, an area where the Maoists are known to operate.

The attack comes after the kidnapping of two Italians by Maoists in the eastern state of Orissa two weeks ago. One of the Italians has subsequently been released, while the state government is still negotiating the release of the other.

According to the BBC, Tuesday's blast occurred in Maharashtra's Gadchiroli district, an isolated area and a known rebel strong hold.

Fifteen CRPF [Central Reserve Police Force] are dead, force spokesman BC Khanduri told Agence-France Presse.

The attack happened around 11:30 am (06:00 GMT) when the bus carrying them struck an IED. The injured are now being taken to hospital. We don't have an exact estimate for the number of injured yet.

The blast occurred in a wooded area, according to reports, and was so powerful it could be heard several miles away.

The Maoists, who began their rebellion in the late 1960's, control a band of Indian territory known as the red corridor that stretches from the north-east to central India.

Indian Prime Minister Manmohan Singh has repeatedly warned that Maoist insurgents in India -- who are especially active in the northeastern part of the country, represent the biggest security threat to India.