Russia on Tuesday expressed its doubts over Iran's claim that it has launched nuclear fuel enrichment "on an industrial scale," the Itar-Tass news agency reported.

"We have certainly heard the Iranian president's statement and take seriously all that is happening with the Iranian nuclear program...However, we want to be guided not by emotional political gestures, but by facts," the Itar-Tass news agency quoted Foreign Minister Sergei Lavrov as saying.

Earlier Monday, Iranian President Mahmoud Ahmadinejad announced that Iran has begun enriching uranium with 3,000 centrifuges and is capable of enriching nuclear fuel "on an industrial scale."

Lavrov said Russia was analyzing the situation along with experts from the International Atomic Energy Agency (IAEA) working in Iran.

"So far we have no confirmation that practical enrichment has begun on new cascades (of centrifuges)," he said.

Russian Foreign Ministry spokesman Mikhail Kamynin also said on Tuesday that Russia is taking the Iranian statement "with all seriousness," Itar-Tass reported.

Such claim "cannot be regarded as the reflection of its leadership's readiness to strengthen cooperation with the IAEA and fulfill decisions by the UN Security Council with the aim of restoring trust in its nuclear program," he said.

The UN Security Council passed two resolutions last December and in March, urging Iran to halt all enrichment-related and reprocessing activities.

Iran's threat to withdraw from the Nuclear Weapons Non-Proliferation Treaty (NPT) also raised "special concern," the spokesman noted.

The Iranian top nuclear negotiator Ali Larijani on Monday warned that Tehran could retreat from the NPT if international community imposes further pressure over its nuclear program.

The United States has accused Iran of trying to develop nuclear weapons under the cover of a civilian nuclear program. But Iran has denied the charges.

Washington said Monday that it hopes to resolve Iran's nuclear issue through diplomatic channels and will gradually increase the diplomatic pressure on Tehran.