Kolkata, Dec 27 (IANS) The Communist Party of India-Marxist (CPI-M) Monday said Home Minister P. Chidambaram should explain how the media came to know about his letter to West Bengal Chief Minister Buddhadeb Bhattacharya while he got it three days later.

"This is a strange way of communication between the union home minister and the chief minister of a state. The media is fully briefed about the letter even before the chief minister gets it," said a CPI-M statement.

Chidambaram had said in the letter that complaints received by the central government "indicate that armed cadres of the CPI-M were deployed in a covert manner under the guise of 'village protection groups' to guard against Naxal (Maoist) attacks.

"There is evidence to show that the camps are mostly located in CPI-M offices and those of local cadres. It is a matter of grave concern that these cadres have been provided with firearms," he had said.

Alleging that the purpose of the letter was to serve the interests of the Trinamool Congress, the state's main opposition party, the CPI-M said that the media was briefed about it Dec 24.

"These reports appeared in the media Dec 25, after being briefed about its contents on the 24th," it said.

Official sources said the letter was received by the government after 11 a.m. Monday.

"This shows that the purpose of the letter is to serve the political interests of the Trinamool Congress, which is part of the union government. The union home minister owes an explanation for this partisan approach," said the statement.

Chidambaram had also said that it was "a matter of grave concern that the political cadres have been given arms in the state. The violence presented an alarming picture, completely unacceptable in a democratic system".

The minister added that if these cadres "continue to take upon themselves the duties of maintaining law and order, I wonder what is the role of security forces, specially central paramilitary forces which have been deployed at the request of the state government".