The self-proclaimed head of the "People's Republic of Donetsk" in eastern Ukraine on Monday declared the region a sovereign state and asked Russia to consider allowing it to accede.

"Proceeding from the expression of the will of the people of the Donetsk People's Republic and in order to restore historical justice, we ask the Russian Federation to consider the issue of the Donetsk People's Republic becoming part of the Russian Federation," Denis Pushilin told reporters.

European Commission presidential candidate Jean-Claude Juncker on Monday warned Ukraine would not make it into the European Union for at least a decade due to its political crisis that has turned violent.

"I do not think the conditions are in place for Ukraine to become a member in the next 10 to 15 years, much less to make Ukraine a member of NATO," Juncker said in a public address in Madrid.

A day after the people of Donetsk apparently voted overwhelmingly to split from Ukraine, an eerie calm reigned on the streets as people wondered what country they had woken up in.

Unlike a similar referendum in the peninsula of Crimea, annexed by Russia in March, there were no wild celebrations, no sense of joy -- just slight confusion about the future and a lingering anger towards the leaders in Kiev.

The European Union ramped up sanctions over the Ukraine crisis on Monday, adding two Crimean firms and 13 people to an existing blacklist, EU diplomats said.

No details were immediately available, but sources said the targets agreed by EU foreign ministers included two Crimean firms expropriated following the much-condemned annexation of the peninsula by Russia in March.

French President Francois Hollande said in Azerbaijan Monday that cooperation between Europe and ex-Soviet countries should not be seen as infringing on anyone else's interests, a clear reference to Moscow amid the crisis in Ukraine.

"The European Union's Eastern Partnership is not directed against anyone, but should encourage greater trade and investment", the French leader said after meeting with Azerbaijani counterpart Ilham Aliyev.

International Monetary Fund chief Christine Lagarde warned in a German newspaper interview Monday that the Ukraine crisis could have "severe" economic consequences for other countries.

Lagarde also told the Handelsblatt business daily that a 17-billion-dollar aid package granted to Ukraine by the IMF would not be enough.

Several explosions and gunfire could be heard near the flashpoint eastern Ukrainian town of Slavyansk Monday, according to an Agence France Presse reporter there, as Kiev seeks to flush out pro-Moscow rebels holed up there.

Fighting broke out in a nearby village on the "front line" of the siege of the town of at least 110,000 people amid what Kiev calls an "anti-terrorist" operation, a rebel spokeswoman said.

Russia raised the stakes in the Ukraine crisis on Monday by saying it respected what rebels claimed was a resounding vote in favor of self-rule in the east of the country.

But the Kremlin also called for dialogue between authorities in Kiev and rebel leaders, as European Union ministers prepared to meet in Brussels to consider toughening sanctions on Russia.

Ukraine's interim president on Monday slammed the rebel-held "referendum" in two eastern regions as a "propaganda farce without any legal basis" that sought to cover up serious crimes.

"The farce that terrorist separatists call a referendum is nothing more than propaganda to cover up murders, kidnappings, violence and other serious crimes," Oleksandr Turchynov told Ukraine's parliament.

Pro-Russian rebels claimed voters in eastern Ukraine massively backed independence in a disputed poll that Kiev and the West dismissed as an illegal "farce", with complete results awaited Monday.

A total of 89 percent of voters cast ballots in favour of self-rule in the Donetsk province, one of two regions holding "referendums" on Sunday, according to the insurgents' self-styled electoral commission.