Pakistan has strongly criticised remarks by the head of the UN nuclear watchdog that its nuclear weapons could fall into the hands of Islamist groups.
Pakistan has a number of nuclear-capable missiles
The concerns were expressed by Mohamed ElBaradei, head of the International Atomic Energy Agency (IAEA), in an interview with Al-Hayat newspaper.
He was quoted as saying he feared that an extremist regime could take root in Pakistan, which has up to 40 warheads.
The military insists that its nuclear weapons security is "foolproof".
"Pakistan is a responsible nuclear weapon state," a Pakistani foreign office statement said.
In 2004 AQ Khan admitted to passing nuclear secrets
"Our nuclear weapons are as secure as that of any other nuclear weapon state. We therefore believe that statements expressing concern about their safety and security are unwarranted and irresponsible."
Foreign Office spokesman Mohammad Sadiq added that Mr ElBaradei should "be careful about his statements and ought to remain within his mandate".
He accused the international media of instigating a "propaganda campaign against Pakistan and its national institutions" following opposition leader Benazir Bhutto's murder at an election rally in December.
"The statements intend to see Pakistan destabilised. This campaign in certain sections of the international media is further upsetting the people of Pakistan, who are still in a state of shock."
Correspondents say that concerns over Pakistan's nuclear security are rising. The country is a key ally of President Bush in his "war against terror".
Those fears have increased after last month's assassination of Benazir Bhutto.
Mr ElBaradei told the pan-Arab daily Al-Hayat newspaper on Tuesday that he was "worried that nuclear weapons could fall into the hands of an extremist group in Pakistan or in Afghanistan".
"I fear that chaos... or an extremist regime could take
root in that country [Pakistan] which has 30 to 40 warheads."
President Musharraf is a key player in the "war on terror"
American presidential hopeful Hillary Clinton said over the weekend that she would support a joint US-British team to oversee the security of Pakistan's nuclear arsenal if she was elected later this year.
"So far as we know right now, the nuclear technology is considered secure, but there isn't any guarantee, especially given the political turmoil going on inside Pakistan," she said.
Pakistan insists that it is a responsible nuclear state, pointing out that its civilian nuclear programme is under IAEA safeguards, and that it has abided by all its IAEA obligations.
But the security of the country's nuclear programme - which started in the early 1970s - has been an international worry since the 1990s when suspicions arose that the country foremost nuclear scientist, AQ Khan, was selling nuclear secrets to Iran, Libya and North Korea.
He admitted that he had been in 2004.