Pakistan on Sunday angrily rejected a report that it had been moving its nuclear weapons in unsafe conditions, saying nobody should underestimate its capability to defend itself.

Two US magazines reported Friday that Pakistan has begun moving its nuclear weapons in low-security vans on congested roads to hide them from US spy agencies, making the weapons more vulnerable to theft by Islamist militants.

The Atlantic and the National Journal, in a joint report citing unnamed sources, wrote that the US raid that killed Al-Qaeda chief Osama bin Laden in May at his Pakistani compound reinforced Islamabad's longstanding fears that Washington could try to dismantle the country's nuclear arsenal.

But in a statement, Pakistan's foreign ministry said the report was "pure fiction, baseless and motivated. It is part of a deliberate propaganda campaign meant to mislead opinion."

Pakistan has consistently rejected concerns over the safety of its nuclear arsenal and alluded to a smear campaign.

"The surfacing of such campaigns is not something new. It is orchestrated by quarters that are inimical to Pakistan," said the statement.

The ministry said Pakistan was capable of defending itself.

"No one should underestimate Pakistans will and capability to defend its sovereignty, territorial integrity and national interests."

After the bin Laden raid, the head of the Strategic Plans Divisions (SPD), which is charged with safeguarding Pakistan's atomic weapons, was ordered to take action to keep the location of nuclear weapons and components hidden from the United States, the report said.

Khalid Kidwai, the retired general who leads the SPD, expanded his agency's efforts to disperse components and sensitive materials to different facilities, it said.

But instead of transporting the nuclear parts in armoured, well-defended convoys, the atomic bombs "capable of destroying entire cities are transported in delivery vans on congested and dangerous roads," according to the report.

The pace of the dispersal movements has increased, raising concerns at the Pentagon, it said.

The article, based on dozens of interviews, said the US military has long had a contingency plan in place to disable Pakistan's nuclear weapons in the event of a coup or other worst-case scenario.