Russia has asked UN Secretary General Antonio Guterres to intervene in grain talks with Ukraine to facilitate Moscow's exports, Foreign Minister Sergei Lavrov said on Wednesday.

Ukraine and Russia have held talks under Turkish and UN mediation to unblock crucial grain exports, as shipments from Ukrainian ports are disrupted by Moscow's military offensive. 

Lavrov said Moscow had agreed to "basic principles" on a grain agreement with Ukraine, but that Kyiv's delegation had refused to include a clause to protect Russian exports. 

"The UN delegation simply kept silent," he told state media in an interview.

"Yesterday we sent a signal to the (UN) Secretary General, saying how is this possible, this is your initiative after all."

His comments came a day after President Vladimir Putin said on a visit to Iran that the West must remove restrictions on exports of Russian grain.

"We will facilitate the export of Ukrainian grain, but we are proceeding from the fact that all restrictions related to possible deliveries for the export of Russian grain will be lifted," Putin told reporters in Tehran after talks with the presidents of Iran and Turkey. 

Russia's military intervention in Ukraine has hampered shipments from one of the world's biggest exporters of wheat and other grain, sparking fears of global food shortages. 

Russian exports of grain have been affected by Western sanctions imposed on Moscow over the intervention.