U.S. magazine The Atlantic reported that Pakistan was moving around warheads and fissile material at a much greater rate, and they could easily fall into the hands of terrorists.

The cover article of the magazine's December edition, headlined "The Ally From Hell," says nuclear arsenal is often being secretly transported by road in lightly guarded trucks in order to conceal the true size of the Pakistani nuclear arsenal.

The ministry said such reports were "pure fiction, baseless and motivated."

"It is part of a deliberate propaganda campaign meant to mislead opinion," the ministry went on, adding that the reports are "orchestrated by quarters that are inimical to Pakistan."

According to the reports, Pakistan's nuclear arsenal almost doubled in the past years and is currently estimated at more than 100 warheads. The country continues to boost its strategic arsenal despite economic problems and unstable political situation.

Ties between Washington and Islamabad have worsened after U.S. special forces have conducted an operation in which Al Qaeda leader Osama bin Laden was killed. Pakistan was not informed about the operation in advance and said the U.S. abused its ally status and violated the country's sovereignty.

U.S. has repeatedly reproached Pakistan for terrorist groups operating on its territory. In September U.S. ambassador to Islamabad told Pakistan's state radio there was evidence of the Pakistani government's alleged ties with militant groups. Washington also withheld some $800 million in military aid to Pakistan over concerns that the government may have links with militants.

Pakistan announced a nuclear program in 1972. In May 1998 both India and Pakistan have conducted nuclear tests.