WASHINGTON/MOSCOW, April 14 -- U.S. President Barack Obama and his Russian counterpart Vladimir Putin on Monday expressed sharply different views on the escalating unrest in eastern Ukraine, both urging the other side to help stop the turmoil.

According to the White House, in a phone call with Putin at Moscow's request, Obama expressed "grave concern" about Russia's support for the actions of pro-Russia armed groups and called on Putin to convince those groups to leave the buildings they seized in Ukraine and withdraw Russian troops from Ukraine's border to defuse tensions.

But Putin denied that Moscow was interfering in Ukraine and urged the United States to use its influence to prevent bloodshed in Ukraine.

"The Russian side underlined that protests in Donetsk, Lugansk, Kharkov, Slaviansk and other cities in the south-east of Ukraine were the result of the lack of will and inability of the leadership in Kiev to take account of the interests of the Russian and Russian-speaking population," the Kremlin said in a statement.

"President Putin called on Barack Obama to do his utmost to use the opportunities that the United States has to prevent the use of force, and bloodshed," it added.

During the phone talks, Obama lauded Ukrainian government for acting with "remarkable restraint" in responding to Russian officials' rhetoric and Kiev's effort to unify the country by holding presidential elections on May 25.

But Putin said that Kiev should focus its effort on involving all regions and political forces in Ukraine in drawing up a new constitution.

Nevertheless, the two leaders agreed to continue the pursuit of diplomatic means to influence the situation ahead of the international talks on Ukraine scheduled for April 17 in Geneva, Switzerland.

A new wave of unrest has erupted in Ukraine's east since last weekend, as pro-Moscow activists seized several government buildings in the cities of Donetsk, Lugansk and Kharkov, demanding a referendum on autonomy and closer ties with Russia.

The Western powers backed the government in Kiev and have threatened to impose more sanctions on Russia.