Iranian President Ebrahim Raisi has told Russian President Vladimir Putin in a phone call that NATO's expansion was a "serious threat" to the region's security and stability.

"NATO's expansion eastward creates tension and is a serious threat to the stability and security of independent states in various areas," Raisi was quoted by Iranian media as saying following Russia's military attack on Ukraine on Thursday.

The Iranian foreign minister Hossein Amir-Abdollahian had said earlier that NATO and US are to blame for the Ukraine crisis.

Some in Iranian media and hundreds of social media users criticized the government for statements showing support for Russia in invading Ukraine.

"I hope what is happening will benefit peoples and the entire region," Raisi said as war unfolded and there were reports of dozens of Ukrainian civilians killed by Russian attacks.

Russia is an ally and a diplomatic supporter of the Islamic Republic. The two countries intervened in the Syrian civil war and are believed to be responsible for the deaths of tens of thousands of Syrian civilians.

Russia is also supporting Iran in nuclear talks with the United States as it also plays a mediating role between the Biden Administration and Tehran.