In a serious breach of security, hardcore militants lodged in the Varanasi Central Jail have allegedly been in telephonic conversation with officials of Pakistan's Inter Services Intelligence, sources said on Saturday.

The details of the conversation came to light earlier this week during a raid by Intelligence Bureau officials, sources told PTI.

The officials, who have already communicated to their superiors and the Union home ministry about the incarcerated militants' nexus with ISI, were reportedly startled at the incident, especially since a jammer system was in place in the jail, they said.

The collusion of some senior jail officials in facilitating the conversation through mobile phones could not be ruled out, sources said.
The IB officials have gathered details of telephone calls made on three occasions in the last 15 days, they added.

The Union home ministry was probing the matter, the sources said.