By Paul Anderson
BBC correspondent in Islamabad
Pakistan has defended its record as a nuclear-armed state, saying it has strong command-and-control systems.
There is widespread interest in Pakistan's nuclear know-how
The foreign ministry says that there may have been a leak of nuclear technology in the past, but that no information or know-how is leaking now.
Islamabad faces persistent allegations that it has exported nuclear-weapons technology to other countries.
The Pakistani authorities are still holding seven nuclear scientists in relation to the allegations.
An investigation into the alleged leaking of nuclear secrets will be concluded soon.
It follows the release of information provided by Iran about its nuclear programme.
For two months Pakistani investigators have been trying to establish who in the nuclear community, if anyone, proliferated technology or know-how.
Iran, Libya and North Korea are the alleged recipients.
The suspicion is narrowing down to a few scientists, among them the father of Pakistan's
nuclear bomb, Abdul Qadeer Khan.
He is one of several scientists who the authorities say may have acted for personal enrichment and who is still being questioned.
The authorities say that anyone found guilty of breaching laws will be punished harshly but that neither the state nor its institutions were involved.
The Foreign Ministry spokesman, Masood Khan, said following his country's nuclear bomb tests in 1998 it had put in place a strong command-and-control system and a strong export regime.
Mr Khan said that there were several rings of security surrounding strategic assets.
He said that if anything untoward happened, it was long ago.
He also complained that international attention on nuclear leaks was unfairly focused on Pakistan when there were clear indications other countries were also involved.
The spokesman said the black market in nuclear weapons-related sales was a multi-headed monster with tentacles which stretch all around the world.
He said the international community had a responsibility to track down the tentacles.