President Vladimir Putin told German Chancellor Angela Merkel Sunday that the ongoing Crimea referendum does not breach international law.

"Putin said the Crimean population's vote is proceeding in full compliance with international law, in particular with Article 1 of the U.N. Charter that stipulates the principle of equality and self-determination of peoples," the Kremlin website said, citing a telephone conversation between the leaders.

"Russia will respect the choice of Crimean residents," Putin said, adding that he was concerned about the aggravation of the situation in eastern and southeastern regions of Ukraine.

Putin and Merkel also discussed the dispatch of an Organization for Security and Cooperation in Europe (OSCE) mission to Ukraine to monitor the situation.

Kremlin spokesman Dmitry Peskov told reporters that Putin was attending the closing ceremony of the Sochi Paralympic Winter Games, and was updated with the latest developments in Crimea.

Also on Sunday, Russian Foreign Minister Sergei Lavrov confirmed to U.S. Secretary of State John Kerry via a telephone conversation that Moscow's position on Crimea referendum remained unchanged.

Lavrov urged the U.S. side to make full of its influence on Kiev authorities to "stop mass lawlessness and arbitrariness against the Russian speaking population."

"Recently, ultra-nationalist and radical forces stepped up their activities in Ukraine's south-east ... Radicals' actions seriously destabilize the situation," the Interfax news agency quoted Lavrov as saying.

The two diplomats "agreed to continue contacts to search for ways to settle the crisis in Ukraine in order to launch a constitutional reform in the country in respect of all Ukrainian regions."

Crimea, a Ukrainian autonomous republic, is holding a referendum Sunday over its future status. More than 1,000 polling stations will remain open from 8 a.m. to 8 p.m. local time (0600 GMT to 1800 GMT). Endi