FACTBOX - Pakistan's nuclear weapons

REUTERS - Pakistan's nuclear installations are believed to be well enough guarded to prevent a successful attack by Islamist militants, though this remains a "low probability, high consequence" risk.

Here are some facts about Pakistan's nuclear programme:

BACKGROUND:

Pakistan began a programme to obtain nuclear weapons after its defeat by India in a 1971 war which led to the division of the country and the creation of Bangladesh, then East Pakistan.

The army sees its nuclear weapons as essential to offset the conventional superiority of its much bigger neighbour.

India sees its own nuclear weapons as a deterrent against Pakistan and China, which defeated it in a border war in 1962.

NUCLEAR TESTS