"Credible" evidence showed that Iran has engaged in projects and experiments relevant to the development of nuclear weapons, the International Atomic Energy Agency (IAEA) said Tuesday in its latest report on the country's nuclear program.

Photo taken on Aug. 21, 2010 shows a view of the Bushehr nuclear power plant in southern Iran. [Ahmad Halabisaz/Xinhua]

"The information indicates that Iran has carried out activities relevant to the development of a nuclear explosive device," said IAEA Director-General Yukiya Amano in the report.

After strict, comprehensive and reliable evaluation on owned extensive information, IAEA believed that Iran had carried out "organized and systematical" activities "specific to nuclear weapons" at least until the end of 2003, the report said.

The report also hinted that Iran probably was still conducting works related to nuclear weapons development until the end of last year, including trial producing of related components, tests and experiments.

Some of these activities are possibly still in progress, the report said.

The UN nuclear watchdog also expressed its serious concern in the report over the issue that Iran's nuclear program might have military purposes.

The paper contains so far the clearest statement of the IAEA about whether Iran was conducting nuclear programs for military purposes.

However, the paper was still unable to reach a clear-out conclusion about whether Iran is attempting to develop nuclear weapons.

Iran has long insisted that its nuclear activities are solely for peaceful purposes such as meeting the ever-growing energy needs.

Analysts believe that the United States and its western allies will cite the findings in the report to push forward with more severe and crippling sanctions.

Teheran completely rejected the report and insisted that Iran had no nuclear weapon program, criticizing that the IAEA report was "unbalanced, unprofessional and politically motivated".