India building top-secret nuclear facility in Karnataka: report

India is building a top-secret facility in southern Karnataka to augment its nuclear power for civilian use as well as increase and upgrade its weapons in a move that could ''deeply unsettle'' its neighbours, says an exhaustive report in international magazine Foreign Policy.

It says work on the project began early in 2012 when tribal pastureland was blocked off with a barbed-wire fence at Challakere for ''a project that experts say will be the subcontinent's largest military-run complex of nuclear centrifuges, atomic-research laboratories, and weapons - and aircraft-testing facilities when it's completed, probably sometime in 2017''.

Foreign Policy listed the project's primary aims: to expand the government's nuclear research, to produce fuel for India's nuclear reactors, and to help power the country's fleet of new submarines.

''But another, more controversial ambition, according to retired Indian government officials and independent experts in London and Washington, is to give India an extra stockpile of enriched uranium fuel that could be used in new hydrogen bombs, also known as thermonuclear weapons, substantially increasing the explosive force of those in its existing nuclear arsenal,'' the report says.

The magazine points out that New Delhi has never published a detailed account of its nuclear arsenal, which it first developed in 1974.

According to independent estimates, India has between 90 and 110 nuclear weapons, as compared to Pakistan's estimated stockpile of up to 120. China has approximately 260 warheads.

The report says China and Pakistan would see the secret project as a provocation. ''Experts say they might respond by ratcheting up their own nuclear firepower. Pakistan, in particular, considers itself a military rival, having engaged in four major conflicts with India, as well as frequent border skirmishes.''

Foreign Policy quotes Gary Samore, who served from 2009 to 2013 as the White House coordinator for arms control, as saying: ''I believe that India intends to build thermonuclear weapons as part of its strategic deterrent against China.''

Other than the Challakere project, Western monitoring agencies were keeping an eye on a similar nuclear facility near Mysore.

''However, Western knowledge about how India's weapons are stored, transported, and protected, and how the radiological and fissile material that fuels them is guarded and warehoused - the chain of custody - remains rudimentary,'' the report says.