Pakistan's nuclear facilities have been attacked three times by home-grown extremists over the past two years, but there is "no waning confidence regarding the safety of the Pakistani nuclear programme",
reported citing a senior US official.
Three separate facilities in Pakistan - each of which deals in some part with nuclear activity - have been targeted by extremists, the unnamed official told the news channel confirming a report in West Point's Combating Terrorism Centre Sentinel.
The report described an attack on a nuclear missile storage facility at Sargodha on November 1, 2007, and a homicide bombing at the nuclear airbase at Kamra on December 10, 2007.
The report also notes a much larger raid by the Pakistani Taliban on August 20, 2008, when homicide bombers blew up several entry points to an armament complex at the country's main nuclear facility, the Wah Cantonment Ordnance Complex.
FOX News cited an unnamed Pakistani official as saying the report was "out of context" but stopped well short of saying the attacks did not occur. "Pakistan's nuclear facilities are safe - there is no likelihood of terrorist activity at those sites," he said.
The US official said it was not clear whether the attackers knew what they were targeting - and added that they would need to do much more to take control of Pakistan's nuclear arsenal.
"We are of the view these incidents did occur but we are not sure you can extrapolate a downgrade of security surrounding the Pakistani nuclear arsenal," he said.
But resurgent jihadists in Pakistan still have the US worried over the safety of the country's nuclear weapons.
"The challenge to Pakistan's nuclear weapons from Pakistani Taliban groups and from Al Qaeda constitutes a real and present danger," writes Shaun Gregory, director of the Pakistan Security Research Unit at the University of Bradford in Britain, in the West Point report.
Gregory's paper, "The Terrorist Threat to Pakistan's Nuclear Weapons", notes that Pakistan's nuclear infrastructure was developed to ward off external attacks from India - not internal strikes from groups like the Taliban.