Russia's foreign ministry has promised it would offer strong assistance to Ukraine to overcome its crisis, but emphasised that the ultimate responsibility for reducing tensions lies with Ukrainians rather than outsiders.

The statement on Saturday came two days after top diplomats from Ukraine, Russia, the United States and the European Union called for an array of actions including the disarming of armed groups and the freeing of public buildings taken over by people on both sides.

In the statement, the Russian Foreign Ministry said deputy minister Grigory Karasin met with Oleg Tsaryov, a pro-Russia candidate in the Ukrainian presidential election that is to take place on May 25.

"The Russian side noted that the questions of resolving the internal political crisis should be decided by Ukrainians themselves in close cooperation with a special monitoring mission" of the Organisation for Security and Cooperation in Europe, the statement said.

"Russia is prepared to show the most wide support in this."

The statement did not specify what that support would be, and it was not clear what it can do or would be willing to do.

Russia denies claims that it has agents in eastern Ukraine directing or encouraging the armed groups.

The emphasis on Ukrainians' responsibility echoed a ministry statement a day earlier which said the first step should be the disarming of members of the ultranationalist Right Sector group, whose activists are occupying buildings in the capital Kiev.

Military forces

Mutual disarmament seems to be in jeopardy, however, as pro-Russian armed groups occupying police stations and other government buildings in eastern Ukraine have said they would not vacate unless the country's acting government resigned.

They say the Kiev authorities, who took power after pro-Russia Ukrainian President Viktor Yanukovych was ousted in February following months of protests, aim to suppress the country's Russian-speakers.

In response to this accusation on Friday, the interim prime minister and president pledged to afford the Russian language a "special status" in Ukraine in a bid to save the deal.

Russia, meanwhile said military forces near the border with Ukraine have been deployed there in response to instability in the country, Reuters news agency reported.

The Kremlin's explanation was a departure from previous statements that the troops were there on routine exercises.

"We ... have forces in the region of the Ukrainian border. Some of these forces are based there permanently, others are there to reinforce, against the backdrop of what is happening in Ukraine itself," Dmitry Peskov, spokesman to Russian President Vladimir Putin said on the Rossiya 1 television station.

He said as a sovereign state, Russia was free to deploy troops anywhere on its territory without restrictions.

He denied allegations that the Russian military was interfering in events inside Ukraine territory.