According to a Sputnik correspondent, his plane has landed in Geneva.
Earlier in the day, Lavrov said he would return to Switzerland after having left Monday evening for meetings in Moscow. Russia's top diplomat stated that he would be present at the final meeting of P5+1 group foreign ministers.
Tuesday is the self-imposed deadline for establishing a political framework for an agreement ensuring the peaceful nature of the Iranian nuclear energy program.
Initially, Tehran insisted on having at least 10,000 centrifuges, but in February agreed to consider a US proposal of cutting the number to 6,500.
Iran and the P5+1 group have held several rounds of talks on Tehran's nuclear program since November 2013 with limited results. The negotiators are now working towards the July 1 deadline to forge a final agreement.