ANKARA

Iran on Monday officially began the process of producing 20 percent enriched uranium at its underground Fordow nuclear facility, according to state media.

"Iranian President Hassan Rouhani had in recent days ordered the implementation of the Strategic Action to Lift Sanctions law. Accordingly, the gas injection process started a few hours ago, and the first UF6 enriched uranium product will be achieved within a few hours," government spokesman Ali Rabiei said.

Rabiei stressed that the whole process started after informing the International Atomic Energy Agency (IAEA).

Iran on Saturday confirmed a plan to increase uranium enrichment up to 20 percent as it moves to implement a recently introduced law as a counter-measure against US sanctions.

In an interview with the state television, the chief of Iran's nuclear agency, Ali Akbar Salehi, said that Tehran has written to the UN nuclear watchdog IAEA about the enrichment plan.

On Friday, the IAEA said Iran had communicated its intention to enrich up to 20 percent purity, a level it achieved before the 2015 nuclear deal between Iran and world powers.

Under the 2015 nuclear deal, Tehran was allowed to enrich uranium up to 3.67 percent. The threshold was, however, breached by Iran in response to the US withdrawal from the deal, raising the level to 4.5.

The plan to increase the level from 4.5 to 20 percent, which is considered "highly enriched uranium", had been in the pipeline for some time but the final trigger was the assassination of prominent Iranian scientist Mohsen Fakhrizadeh in November.

Following the incident that drew strong reaction from Iran, the country's parliament introduced a strategic plan to counter sanctions, which called for accelerating nuclear activities and ending voluntary implementation of the Additional Protocol.

The bill was finally turned into a law after the country's top supervisory body, the Guardian Council, gave its approval, despite resistance from the government.

The implementation of the plan is likely to further heighten tensions between Iran and the West at a time when the new administration in Washington had hinted at the possibility of US returning to the 2015 accord.

The Rouhani government says it is willing to return to full compliance of the deal, which means scaling down uranium enrichment back to 3.6 percent, if the US "unconditionally" returns to the deal.

Tensions have been running high between Iran and the US, especially in the restive Persian Gulf and Iraq, in recent weeks, on the first anniversary of the killing of Iranian commander Qasem Soleimani in a US airstrike.