Pranab Mukherjee in Delhi. Picture by Rajesh Kumar

New Delhi, Oct. 23: The arrest of two soldiers on charges of spying is reason to believe that Pakistan’s Inter Services Intelligence (ISI) has penetrated the armed forces, defence minister Pranab Mukherjee said today.

“We have begun our own exercises to unravel the spy rings,” said Mukherjee. He was “deeply concerned that there were spies in the army”.

The investigations have revealed an ISI-backed network operating between New Delhi and Kathmandu. “We are trying to find out more. A detailed investigation is necessary. We have to ensure such things don’t happen again,” he said.

Neither of the two soldiers arrested is senior enough to have access to classified information of operational and strategic importance. They were arrested by the Delhi police special branch acting with the Intelligence Bureau (IB).

The IB suspects the two would have developed their own sources in the army through personal contact with fellow soldiers, some of whom would have functioned as couriers and messengers involved in physically transferring files and data between different offices.

The defence minister said efforts were being made to trace the spy-ringmasters. “We are trying to nail the kingpins,” he said, raising the possibility of arrests of personnel more senior than the two soldiers.

Anil Kumar Dubey and Ritesh Kumar Vishwakarma were arrested at the weekend but the investigations were yet to determine if both were members of the same spy ring. It was the IB that had begun an investigation that led to the arrests. Delhi Police had said yesterday that the arrests were not related.

There was still not enough evidence that both were engaged in the same “module”. But military sources said they were still trying to unearth information. “We cannot comment when investigations are on,” one senior officer said.

Mukherjee said there were repeated checks within the services. “If there is suspicious activity, the suspects are immediately placed under surveillance and that is how we caught these two men,” the defence minister said.