Pakistan says it has tightened security around all its nuclear facilities following a surge of militant attacks within its borders.

The head of the agency that handles Pakistan's nuclear arsenal, Khalid Kidwai, told foreign reporters Saturday that, in his words, "the state of alertness has gone up." 

However, he said there is no conceivable scenario in which Pakistan will fall to al-Qaida or Taliban type extremists.

Militant groups have launched a rising number of attacks on Pakistani security forces and intelligence personnel in recent months.

Pakistan is estimated to have about 50 nuclear weapons.

Some information for this report was provided by AFP, AP and Reuters.