SRINAGAR: Four Indian police officers have been arrested in Kashmir for alleged links with rebels fighting against Indian rule, the police chief of the disputed Himalayan region said Monday.

The case has rattled Indian authorities who administer the tense region, where insurgents have waged a violent campaign for decades demanding independence or a merger with neighboring Pakistan.

The alleged rebel ties were discovered last week during a routine investigation into a recent shooting attack on a former militant, police chief Rajendra Kumar said.

Authorities have arrested two intelligence officials and two low-ranking police officers, and two more suspected officers are still at large, he said.

Kumar said the six are believed to have links to Kashmir's largest militant group, Hizbul Mujahideen. Officials are investigating whether they might have helped rebels stage attacks, procure arms, avoid arrest or move undetected through the region.

One of the suspects, a constable who has worked undercover infiltrating rebel groups in the past, was arrested briefly in 2008 for allegedly buying cell phone cards used by gunmen in deadly attacks that year in Mumbai. However, the constable, Mukhtar Ahmed, was released after authorities said he had made the purchase as part of his undercover work.

Ahmed's re-arrest follows new evidence that suggests he may have operated outside of his official mandate on behalf of the rebels, Kumar said.

This is not the first time Indian law enforcement officers have been implicated in rebel activities in Kashmir, where some 700,000 Indian troops are deployed for a population of 12.5 million.

In 2006, three Indian soldiers and two police officers were detained for alleged links with the rebel group Lashkar-i-Taiba, which New Delhi blames for the Mumbai attacks. The two police officers were removed from service, while the army has remained quiet about the status of the detained soldiers.

In 1992, two policemen and a paramilitary soldier were arrested for allegedly helping rebels bomb the police headquarters in Srinagar in an attack that killed one officer and injured several others.

Though an insurgency launched in 1989 has largely been suppressed, attacks still occur, along with frequent street protests. About 68,000 people have died in rebel violence and ensuing crackdowns.

Pakistan also controls part of Kashmir and, like India, claims the entire region.