Russian President Vladimir Putin told Iran's foreign minister on Monday there was no justification for the U.S. bombing of his country and that Moscow was trying to help the Iranian people.

Putin hosted Iranian Foreign Minister Abbas Araqchi in Moscow two days after U.S. President Donald Trump sent U.S. bomber planes to strike Iran's three main nuclear sites.

"The absolutely unprovoked aggression against Iran has no basis and no justification," Putin told Araqchi in televised comments.

"For our part, we are making efforts to assist the Iranian people," he added.

"I am very glad that you are in Moscow today, this will give us the opportunity to discuss all these pressing issues and think together about how we could get out of today's situation."

Araqchi told Putin that Iran was conducting legitimate self-defense, and thanked Russia for condemning the U.S. actions. He conveyed best wishes to Putin from Iran's supreme leader and president.

"Russia is today on the right side of history and international law," said Araqchi.

It was unclear, however, what Russia might do to support Iran, an important ally with which Putin signed a strategic cooperation treaty in January. That agreement did not include a mutual defense clause.

Before Saturday's U.S. strikes, Moscow had warned that U.S. military intervention could destabilize the entire region and plunge it into the "abyss."

Asked what Russia was ready to do to help Tehran, Kremlin spokesman Dmitry Peskov said: "It all depends on what Iran needs." He said the fact that Moscow had offered to mediate in the crisis was itself a form of support.

Peskov condemned the U.S. attacks.

"An increase in the number of participants in this conflict is happening - or rather, has happened. A new spiral of escalation of tension in the region," Peskov told reporters.

"And, of course, we condemn this and express regret in this regard, deep regret. In addition, of course, it remains to be seen what happened to (Iran's) nuclear facilities, whether there is a radiation hazard."

Peskov said Trump had not told Putin in detail about the planned strikes in advance.

"There was no detailed information. The topic of Iran itself was repeatedly discussed by the presidents during their most recent conversations, certain proposals were voiced by Russia, but there was no direct detailed information about this," he said.