"[Moscow] is deeply saddened by the news of the tragic death of Raisi and the head of the Iranian Foreign Ministry in a helicopter crash," Lavrov said in a statement, adding that Russia "sincerely condoles with the families and friends of the victims, as well as all the friendly people of Iran."
"We will always remember these outstanding political figures as true patriots of the Islamic Republic who firmly defended the interests of their state and gave their lives in selfless service to their motherland," Lavrov said.
"In Russia, President of Iran Ebrahim Raisi and Minister of Foreign Affairs of Iran Hossein Amirabdollahian were known as true, reliable friends of our country. Their role in strengthening mutually beneficial Russian-Iranian cooperation and trustful partnership is invaluable," Lavrov added.
The Russian Embassy in Tehran also expressed condolences to Iran and said that it found out about the tragedy with "great sadness."
"We were very anxious to help, and Russian rescuers from [the Russian Ministry of Emergency Situations] EMERCOM were sent to Iran on an emergency basis by decision of Russian President [Vladimir Putin]. We offer our sincere condolences to the families and friends of the victims, to the entire Iranian people and government," the embassy said on Telegram.
The embassy wished "patience and fortitude in overcoming this most serious tragedy" to Iran, adding that "as a sign of solidarity with Iranian friends" the flag of the Russian diplomatic mission would be lowered.
Earlier in the day, Iranian Vice President Mohsen Mansouri confirmed media reports that Raisi and his delegation, including Foreign Minister Amirabdollahian, died in a helicopter crash in northwestern Iran.