Pakistan's nuclear sites have been attacked three times within the past two years, according to the Times of India.
Terrorism experts warn these previous attacks have not received enough attention by the Pakistani government. They are concerned, because the nuclear sites are close to areas dominated by Taliban militias and al-Qaeda.
But Pakistan insists that its nuclear weapons are fully secure and there is no chance of them falling into the hands of extremist groups or terrorists.
Shaun Gregory, a professor at Bradford University in the United Kingdom, has studied the attacks. He said they were conducted by Pakistan's own home-grown terrorists.
"These attacks have occurred even as Pakistan has taken several steps to secure and fortify its nuclear weapons against potential attacks, particularly by the United States and India." Gregory said.
Gregory also points out in his paper, first published in the West Point's Counter Terrorism Center Sentinel, "despite these elaborate safeguards, empirical evidence points to a clear set of weaknesses and vulnerabilities in Pakistan's nuclear safety and security arrangements."
Source: Times of India