SRINAGAR, India - One of the two Indian men arrested for illegally buying mobile phone cards used by the gunmen in the Mumbai attacks was a counterinsurgency police officer who may have been on an undercover mission, security officials said yesterday, demanding his release.

The arrests, announced in the eastern city of Calcutta, were the first since the bloody siege ended. But what was touted as a rare success for India's beleaguered law-enforcement agencies quickly turned sour as police in two Indian regions squared off against one another.

Senior police officers in Indian Kashmir, which has been at the heart of tensions between India and Pakistan, demanded the release of the officer, Mukhtar Ahmed, saying he was one of their own and had been involved in infiltrating Kashmiri militant groups.

Indian authorities believe the banned Pakistani-based militant group Lashkar-e-Tayyaba, which has links to Kashmir, trained the gunmen and plotted the attacks in Mumbai that began Nov. 26.

The implications of Ahmed's involvement - that Indian agents may have been in touch with the militants and perhaps supplied the SIM cards used in the attacks - added to the growing list of questions over India's ill-trained security forces.

Earlier yesterday, Calcutta police announced the arrests of Ahmed and Tauseef Rahman, who allegedly bought SIM cards by using fake documents, including the identification cards of dead people. The cards allow users to switch their cellular service to phones other than their own.

Rahman, of West Bengal state, later sold them to Ahmed, said Rajeev Kumar, a senior Calcutta police officer.

Both men were arrested Friday and charged with fraud and criminal conspiracy, Kumar said, adding that police were investigating how the 10 gunmen obtained the SIM cards.

But the announcement had police in Srinagar, the main city in Indian-controlled Kashmir, fuming.

They told Calcutta police that Ahmed is "our man and it's now up to them how to facilitate his release," said one senior officer speaking on condition of anonymity. Other police officials in Kashmir supported his account.

The officer said Ahmed was a Special Police Officer, part of a semiofficial counterinsurgency network whose members are usually drawn from former militants. The force is run on special funding from the federal Ministry of Home Affairs.

"Sometimes we use our men engaged in counterinsurgency ops to provide SIM cards to the [militant] outfits so that we track their plans down," said the officer.

Police said Ahmed was recruited to the force after his brother was killed five years ago, allegedly by Lashkar-e-Tayyaba militants for being a police informer.

About a dozen Islamic militant groups have been fighting in Kashmir since 1989, seeking independence from mainly Hindu India or a union with Muslim-majority Pakistan.

The bungling and miscommunication among India's many security services come as police said they were re-examining another suspected Lashkar militant who was arrested nine months before the attacks carrying hand-drawn sketches of Mumbai hotels, the train terminal and other targeted sites.