"Both sides dismiss as totally baseless a Western media report alleging that Iran had admitted to the IAEA (International Atomic Energy Agency) that Pakistan had given Iran assistance for its nuclear program," Pakistan's foreign ministry said in a statement.
The statement was issued after Iran's Deputy Foreign Minister Gholam Ali Khoshru held talks in Islamabad late Thursday with Pakistan's acting foreign secretary Tariq Osman Hyder.
It cited a report carried in the Times of London newspaper Thursday saying Iran admitted receiving nuclear help from Pakistan, and an earlier report in the same daily saying Pakistan had given nuclear assistance to Iraq.
"These unsubstantiated reports are published periodically in some sections of the Western media, and they reflect their longstanding anti-Muslim bias," the statement said.
Pakistan went public as a nuclear power in May 1998 when it conducted a series test nuclear explosions after similar tests by rival India.
International nuclear experts estimate it has an arsenal of 30 to 60 nuclear warheads.
The United States has accused Iran of seeking to procure atomic weapons under cover of a civilian program. The IAEA, the UN's nuclear agency, found in a recent report there was no proof Iran had nuclear weapons.
The United States rejected the IAEA report as "impossible to believe."
The board of the IAEA will meet in Vienna on November 20 to consider the report.
If it finds Iran to be in violation of the nuclear Non-Proliferation Treaty (NPT), it could refer the matter to the UN Security Council.
Iran warned Thursday such a referral, which could lead to sanctions, would result in an "international crisis."