Russian President Vladimir Putin has called for an 'immediate halt' to fighting in the eastern Ukrainian city of Donetsk.
In his first comments since new Ukraine president Petro Poroshenko was elected on Sunday Putin urged Kiev to start talks with rebel leaders.
But the Ukrainian government has accused Russia of sending "terrorists" across its border.
Ukraine's foreign ministry said: "There are grounds to believe that Russian terrorists are being sent onto Ukrainian territory, organised and financed under the direct control of the Kremlin and Russian special forces."
Russian President Vladimir Putin has dismissed talk of a new Cold War over the Ukraine crisis.
The former KGB agent blamed the unrest in the country on the West and said sanctions on the US and European Union would rebound.
He also denied trying to rebuild the Soviet Union after reclaiming Crimea and pledged he would work with whoever is elected in Ukraine this weekend.
"I would not like to think this is the start of a new Cold War. It is in no one's interest and I think it will not happen," he said.
The crisis has plunged East-West relations to their lowest level since the Cold War ended in 1991.
Vladimir Putin has said he is concerned that "radicals" in Ukraine may try to disrupt the supply of natural gas from Russia to Europe.
"I won't deny that we are seriously worried by Ukrainian radicals' statements and open threats to hinder gas transit. We still hope common sense will prevail there," the Russian president said.
Many European nations depend on Russian gas that flows through pipelines in Ukraine.
Russian President Vladimir Putin turned salesman today on a high-profile trip to China, where he was trying to secure a £240 billion gas deal.
After the Ukraine crisis, the President wants to find new markets for Russian gas.
ITV News China Correspondent Lucy Watson reports.
Russian President Vladimir Putin has taken part in an ice hockey match between Russian amateur players and ice hockey stars, at a festival of Russia's amateur hockey.
Donned in a red outfit and pads, the event was organised by the Night Hockey League near the Olympic Park in the Black Sea resort of Sochi, Russia.
The Obama administration has attacked Vladimir Putin over his visit to Crimea today, calling the move "provocative and unnecessary".
The Russian President visited the peninsula, annexed from Ukraine in March, to mark the anniversary of the Soviet Union's victory over Nazi Germany.
US State Department spokeswoman Jen Psaki issued a strong condemnation of the visit, saying:
"This trip is provocative and unnecessary. Crimea belongs to Ukraine and we don't recognize, of course, the illegal and illegitimate steps by Russia in that regard,"
European Ambassadors have agreed in principle to add approximately 15 people and five Crimean-based companies to the Russia sanctions list, diplomats told Reuters.
President Vladimir Putin has hailed the Crimea region joining Russia as he visited the area for the first time since it was annexed from Ukraine in March.
Putin delivered a speech in the city of Sevastopol and watched a parade of Russian navy ships and a flyby of Russian aircraft which marked Victory Day - the World War Two defeat of Nazi Germany.
Ukraine has condemned Putin's visit as trampling on international law and deliberately escalating the crisis.
Russian President Vladimir Putin has attended a Victory Day parade in Sevastopol, Crimea, marking his first visit to the area since it was annexed in March.
His visit to the region is likely to outrage the West and has already been denounced by the Ukrainian government, with the foreign ministry calling it a "deliberate escalation" of the crisis.
Putin flew to Crimea after attending a military parade in Moscow, which was making the anniversary of the World War Two victory over Nazi Germany.
Russian President Vladimir Putin's visit to Crimea is a "deliberate escalation" of the crisis, Ukraine's Foreign Ministry said.