Russian Foreign Minister Sergei Lavrov on Tuesday urged the OSCE to put pressure on Ukraine to implement a roadmap for de-escalating the violence drawn up by the pan-European security body.

"Ukrainian leaders absolutely refuse to implement the (de-escalation) roadmap and we call all countries members of the Organization for Security and Cooperation in Europe to put pressure on Ukrainian leaders," Lavrov told reporters in the Serbian capital.

The United Nations said Monday 34,000 Ukrainians have been forced to leave their homes as a violent pro-Russian insurgency rages in the east of the country.

The U.N. said it had identified 19,000 displaced people in Ukraine, while estimates from local authorities indicated another 15,000 had been forced from their homes in areas it does not monitor.

Five people were killed and another three went missing after a fire swept through an oil refinery in Siberia as a result of a gas explosion, Russian investigators said on Monday.

"As a result of the fire five people were killed, (and) another seven were hospitalized with injuries," the investigative committee said in a statement.

The world needs to take a harder line on Russia after its annexation of Crimea, a Ukrainian minister said Monday at an international conference in Tokyo.

The two-day meeting involving Asian countries and members of the Organisation for Security and Co-operation in Europe comes as tensions flare between the West and Moscow over Ukraine, where pro-Russian forces are fighting against regular troops.

Europe risked gas supply disruptions Monday after Russia rejected an 11th-hour compromise deal and cut supplies to Ukraine in a feud that has further fractured East-West relations.

Ukraine hosted the last-gasp talks hoping to keep an energy shortage from compounding the problems of the new pro-Western leaders as they confront a two-month separatist insurgency threatening the very survival of the ex-Soviet state.

Urgent EU-brokered gas talks between Russia and Ukraine resumed in Kiev on Sunday ahead of a looming threat by Moscow to cut off its neighbor's supplies in a move that could impact Europe, an EU source told Agence France Presse.

Russia's RIA Novosti news agency cited its own source as saying that the first meeting involved EU Energy Commissioner Guenther Oettinger, Ukrainian Prime Minister Arseniy Yatsenyuk and Alexei Miller, the head of Russia's state gas firm Gazprom.

Russian Foreign Minister Sergei Lavrov claimed Sunday that a Ukrainian mob that attacked Moscow's embassy in Kiev wanted to take over the compound and see "blood spilled."

"Our diplomats feel that the attackers wanted to physically seize the embassy," news agencies quoted Lavrov as saying. "There are also reasons to believe that they wanted to see blood spilled."

Russian officials lashed out at Ukraine's foreign minister Sunday after footage showed him using an expletive to describe Russian President Vladimir Putin as he sought to calm angry demonstrators attacking the Russian embassy in Kiev.

Andriy Deshchytsya was filmed by local television being cheered by protesters after telling them "Putin is a prick" in a bid to stop the crowd storming Russia's diplomatic mission Saturday.

Ukrainian security services are holding two Russian television journalists working for a defense ministry outlet after they were detained at a government checkpoint leaving the conflict-hit east of the country, the channel said Sunday. 

The journalists from Russia's Zvezda, or Star channel -- Nikita Konashenkov and Yevgeny Davydov -- were detained Saturday by Ukraine's National Guard as they headed to the airport after covering the fighting in eastern Ukraine between government forces and pro-Russian rebels. 

Russia's foreign minister urged U.S. Secretary of State John Kerry on Saturday to use his influence over Ukraine's leaders to convince them to suspend a military offensive in the separatist east.

Russian Foreign Minister Sergei Lavrov "urged the United States to use its influence with the Kiev authorities to nudge them toward a more realistic assessment of the situation, making them realize the hopelessness of using force to resolve a domestic conflict," the Russian foreign ministry said after the two diplomats spoke by telephone.