Yatensenyuk made a surprise visit to the eastern mining city of Donetsk on Friday, where armed militants have barricaded themselves inside a government building and demanded a referendum to join Russia. They have declared the independent "Donetsk people's republic" and vowed to defend themselves against any attempts to evict them.

Local officials didn't go quite as far, but did ask Yatsenyuk to allow referendums to be held on autonomy for their regions, but not on secession.

"There are no separatists among us," said Gennady Kernes, the mayor of Kharkiv, where protesters occupied a government building earlier in the week.

Yatsenyuk did not say whether it would be possible to hold local referendums without the consent of the government. Ukraine has condemned as illegal last month's referendum in Crimea that led to its annexation by Russia.

Gas tension heats up

Russian President Vladimir Putin put more pressure on Ukraine on Thursday when he told European leaders that gas supplies going through Ukraine would be at risk if the continent didn't help Kyiv pay its mounting debts. His warning came after Russia had already increased Ukraine's energy prices by 81 percent and told Kyiv to rewrite its constitution so that border regions could negotiate with Moscow directly.

Ukraine on Friday said it would ask Europe for help in paying for gas from Russia. Speaking to parliament in Kyiv, Ukrainian Energy Minister Yuri Prodan said the EU would stand with Kyiv if Russia cut off or reduced supplies and would make sure Moscow couldn't increase flows through alternative pipelines to bypass its neighbor.

"Ukraine cannot pay such a political, uneconomic price, so now we are negotiating with the European Union about reverse deliveries into Ukraine," Prodan said.

Putin pledges to fulfill obligations

Putin said on Friday that Russia would fulfill its contractual obligations to send natural gas to Europe.

"We certainly guarantee the fulfillment of our obligations before our European customers in full," the Russian president said in comments released by the Kremlin. "The issue is not about us, the issue is about securing transit through Ukraine."

The EU executive on earlier on Friday had urged Russia to honor its gas contracts. Around a quarter of Europe's gas is purchased from Russia, and half of that is piped through Ukraine.

"Europe is a reliable gas client and we expect our suppliers to meet their commitments," said European Commission spokeswoman Pia Ahrenkilde Hansen.

Commission officials told reporters in Brussels there had been no interruptions to gas supplies so far.

dr/pfd (AFP, Reuters, AP, dpa)