Russian and Iranian negotiators met briefly behind closed doors in Moscow on Tuesday, Russian news agencies reported.
The RIA-Novosti news agency, citing the Iranian state agency IRNA, said the talks had ended by early afternoon and the Iranian delegation had left the city. It said the two sides had agreed to continue consultations.
RIA-Novosti and the Interfax news agency cited an unnamed diplomatic source as saying the talks had taken place Tuesday but gave no information other than reporting that the Iranian side was led by chief negotiator Ali Hosseinitash.
A spokeswoman for the Russian Security Council said she had no information on any talks between Russia and Iran.
Russian Foreign Minister Sergey Lavrov on Monday accused Iran of adopting an unhelpful attitude during talks on Tehran's nuclear program, but said Moscow had agreed to an Iranian request for further consultations.
"Iran in the last day or two appealed to us again to hold consultations," Lavrov told reporters. "They will take place in the nearest future."
Previous talks on Russia's Western-backed offer to host Iran's uranium enrichment program produced no results after Teheran rejected Moscow's demand to suspend uranium enrichment activities at home.
Lavrov reiterated that a halt to enrichment activities was a condition for the proposal, which was seen as a way for Iran to avoid the threat of UN sanctions.
"We are very disappointed with the way Iran has been conducting itself in these negotiations, absolutely not helping those who want to provide for finding peaceful ways to resolve the whole situation surrounding the Iranian nuclear program," Lavrov said.
He said he could not comment on whether Iran has rejected the proposal to enrich uranium for Iran on Russian territory because "contradictory signals are coming from Tehran. One day they reject it, the other day they don't."