Security personnel in Jammu and Kashmir and the Northeast are increasingly encountering technological innovations in explosives planted by militants.

In the last few months, they have stumbled upon improvised explosive devices rigged to go off even if the electrical relay igniting the fuse has been disconnected, a security expert says.

Militants install a second relay in the IEDs so that they explode in the face of the bomb disposal squad personnel, without whom anti-militancy operations are seriously affected.

While security personnel have now found a way to counter the 'double relay' system, IEDs that can be triggered merely by light, sound, smoke, temperature, humidity or even a radio frequency have cropped up.

"Militants find these very effective to target security personnel. For example, they are known to have placed sound-sensitive IEDs on routes to be taken by army convoys and planted light-sensitive ones near security bases at night so that they go off at first light," says an official with the National Bomb Data Centre established by the National Security Guards at its campus in Manesar, Haryana.

The NBDC, one of just six of its kind in the world and the only one in India, has been collecting data on bomb explosions across the country since 2000.

It is not just technologically-advanced IEDs that have been found, innocent-looking objects have also been rigged to explode to extract maximum casualty among civilians.

While the 'transistor bomb' is now passé, bottles of cold drink that go off when the cork is unscrewed and water jugs that explode when the tap is pressed are causing concern.

"It is obvious that IEDs with so much technological inputs could not have been engineered by the militants themselves. They are surely getting hi-tech help, probably from outside the country," says the official.

Since its inception, the NBDC has been collecting, collating, analysing and evaluating all bombings reported in the country with the help of which it can provide advice on the degree of sophistication achieved by militants in various states.

"All security agencies have been asked to send in details of every bomb explosion to the NBDC so that the collated data is exhaustive," the official adds.

Sometimes, teams of the NBDC also visit the sites to gather information so that suggestions on shifts in bombing strategies and preventive security measures for the particular area can be given.