The comments came as key powers were to invite Iran to hold direct talks on its nuclear activities and as Iran marked a national nuclear day.
"What's needed from Iran is that it convinces us all of the exclusively peaceful character of its nuclear programme," Lavrov said in an interview with Russian media outlets including the RIA Novosti news agency.
Underlining Russia's relatively close ties with Iran however, he reiterated Moscow's view that there is no evidence Tehran is trying to develop nuclear weapons.
"There's no evidence that this programme has a military dimension. But several countries and the International Atomic Energy Agency (IAEA) have questions Iran needs to explain," he said.
On Wednesday the United States, Russia and other key powers said they would invite Iran to hold direct talks on the Islamic republic's nuclear programme.
Western nations suspect that Iran is trying to develop a nuclear weapons programme under cover of its stated aim of developing civilian nuclear energy. Iran denies such claims.
Russia has been building a nuclear power station for Iran at Bushehr and is to supply the fuel needed to run the facility, which Iran's critics say means the Islamic Republic should have no need to enrich its own uranium fuel.
