Pakistan intelligence agency Inter Services Intelligence's activities continue to pose a grave threat to the internal security and the southern states need to step up vigil, a senior defence official said on Saturday.

"Recent arrests of ISI operatives and recovery of large caches of arms, ammunition and explosives in the neighbouring states gave credence to our fears," Maj Gen. B Sivasankar, General Officer Commanding in charge of the South said, addressing a civil-military conference in Thiruvananthapuram.

Despite certain degree of immunity enjoyed by Kerala, the state could not ignore these developments as its vast coastline, healthy mix of all communities and porous coastline and border with neighbouring countries and states rendered it vulnerable, he said.

The activities of ISI were assuming serious dimensions and increasing nexus between fundamentalist and criminal fringe elements are creating problems in the hinterland areas.

The ISI was encouraging these elements by providing financial, ideological and material support to them, he said.

Emphasising the importance of sharing of information by intelligence agencies, he noted that Subsidiary Multi Agency Centre had been meeting regularly.

In his brief inaugural address to the meet, Kerala Chief Minister V S Achuthanandan said the state government gave top priority to the welfare of serving and retired soldiers and their families.

Sivasankar said it was of prime importance that the state agencies provided prompt and authentic information about the recruits to the defence forces from Kerala, from where about 2,000 candidates are recruited every year.

"There is need to be very authentic on verification procedures, failing which undesirable and anti-national elements may find their way into the forces," he said.

He also sought the help of the state administration for providing sufficient land required by the defence forces and Coast Guard units in Kerala.

On welfare of serving and ex-service personnel, he wanted more seats reserved for their children in educational institutions in the state.

Kerala Director-General of Police Raman Srivastava and senior civil servants were present at the meet, being held here after a gap of two years.