Russian President Vladimir Putin and his US counterpart Barack Obama have not stopped contact due to the situation in Ukraine, the Kremlin said Saturday.

"The conversation is continuing quite regularly. The previous conversation between the two presidents took place last week," Kremlin spokesman Dmitry Peskov told the Echo of Moscow radio station.

"There are a lot of disagreements now, and therefore these dialogues are sometimes very tough, but nevertheless, communication is continuing."

Some Western media had earlier reported that Putin and Obama had severed their "direct contacts" because of the ongoing crisis in Ukraine.

Russia's Federal Migration Service said Friday the country has introduced border control on the crossing points between its newly-adopted republic of Crimea and Ukraine.

Foreign Minister Sergei Lavrov accused the West of attempting to "capture" Ukraine for geopolitical projects, while US State Secretary John Kerry accused Russia of refusing to take "a single concrete step in the right direction" in the past seven days.

The leaders of the Group of Seven (G7) industrialized nations agreed Friday night to impose more sanctions on Russia over its "inaction" in easing the tension in eastern Ukraine.

Also on Friday, acting Ukrainian Prime Minister Arseny Yatsenyuk accused Russia of violating the compromise Geneva agreement and urged the international community to unite their efforts to secure peace in the world.

The standoff between Russia and Ukraine peaked on Thursday, when Russia began drills near the border with Ukraine in response to Kiev's "anti-terror" operation, which left five pro-Moscow protesters dead.

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