President Vladimir Putin said Thursday that Russia is "still open" to talks on Ukraine's gas debt, accusing the EU of failing to make specific proposals to help prevent a cutoff of supplies from next month.

In an open letter to European leaders, Putin also called on Brussels to "more actively engage" in finding ways to stabilize crisis-hit Ukraine's economy.

Just 10 days before a key presidential election, Ukraine's interim leaders were battling Thursday to keep the country together despite a European peace push, facing a bloody insurrection in the east and a tense standoff with Russia.

Kiev on Wednesday hosted the first round of so-called national unity talks under an OSCE initiative to try to resolve the deepening crisis on Europe's eastern flank and allow the May 25 vote to go ahead.

Pro-Russia protesters disrupted a public meeting with German Chancellor Angela Merkel in Berlin Wednesday, calling for the arrest of "Nazis" in Ukraine.

Around a hundred protesters, wearing caps emblazoned with the Russian two-headed eagle emblem, booed the chancellor and brandished placards bearing slogans such as "Arrest the Nazis in Ukraine" and "No war against Russia".

A university in Venice on Wednesday said Russian Culture Minister Vladimir Medinsky had cancelled a planned visit to collect an award following a protest by students and professors over his nationalist views.

"The minister cancelled his visit. The ceremony has been postponed indefinitely," said Federica Scotellaro, a spokeswoman for Ca' Foscari University.

Russia's state arms exporter on Wednesday praised France for sticking by a contract to build two Mistral warships for the Russian navy despite U.S. objections to the project.

Work in the 1.2 billion euro ($1.6 billion) deal for two Mistral-class helicopter carriers is proceeding on schedule, demonstrating "France's reliability as a partner," a spokesman of Rosoboronexport was quoted by ITAR-TASS as saying.

Ukraine's embattled leaders launched round-table talks Wednesday as part of a Western-backed push to prevent the country falling apart, vowing they would not bow to "blackmail" by pro-Russian rebels waging an insurgency in the east.

The so-called national unity discussions -- which crucially do not involve the insurgents -- are being held barely two weeks before Ukraine holds a presidential election that the West is scrambling to keep alive.

Middle-aged municipal worker Masha bent down in her green parks department overall to tend the pristine flowerbeds on a tree-lined avenue in downtown Donetsk.

"We don't know who will be paying our salaries from now on," she said, digging around in the soil with her trowel.

Among those hit by new sanctions imposed by Brussels on pro-Russian officials are Natalya Poklonskaya, the prosecutor of Crimea who became an Internet sensation for her good looks, and a self-styled mayor of the rebel-held Ukrainian city of Slavyansk.

Vyacheslav Volodin, the hugely influential first deputy chief of Russian President Vladimir Putin's staff, and Vladimir Shamanov, a military commander who gained notoriety for his heavy-handed tactics in volatile Chechnya, were also on a new sanctions list released by the European Union.

Deadly violence flared in the restive east of Ukraine on Tuesday even as Europe stepped up its diplomatic efforts to resolve the escalating crisis on its doorstep.

German Foreign Minister Frank-Walter Steinmeier was in Ukraine to push the Kiev authorities and pro-Moscow rebels to come together at the negotiating table after the East-West security body OSCE drew up a roadmap aimed at easing tensions.

Russian President Vladimir Putin will next week travel to China for a visit expected to see Moscow and Beijing seal a landmark gas agreement, the Kremlin said on Tuesday.

During the May 20 visit to Shanghai, Putin will oversee the signing of a number of "important agreements" in trade and energy, the Kremlin said without providing further details.