The Ukrainian defence ministry says six servicemen have been ambushed and killed and eight others wounded in the country's restive east.

The defence ministry said the troops were attacked outside the town of Kramatorsk on Tuesday afternoon by at least 30 insurgents who were using grenade launchers and automatic weapons.

Pro-Russia insurgents have been capturing government buildings and controlling towns and cities across eastern Ukraine for a month now. Two eastern regions — Donetsk and Luhansk — declared independence on Monday.

Kramatorsk is located about 100 kilometres north of Donetsk, where conflict between pro-Russian separatists and other Ukrainians has been common. 

Earlier Tuesday Germany's foreign minister tried to broker a quick launch of talks between Ukraine's central government in Kyiv and the pro-Russia separatists who declared independence a day ago in two eastern regions.

Ukraine

German Foreign Minister Frank-Walter Steinmeier, right, talks with his Ukrainian counterpart Andrii Deshchytsia during his visit to Kiev, Ukraine, on Tuesday. (Andrew Kravchenko/Associated Press)

Speaking at Kyiv's main airport, envoy Frank-Walter Steinmeier said Germany supports Ukraine's efforts to arrange for a dialogue between the central government and its opponents in the eastern Donetsk and Luhansk regions that form the nation's industrial heartland.

Pro-Russia insurgents have seized government buildings, clashed with government forces and have captured a number of hostages across eastern Ukraine during the past month. Steinmeier voiced hope for a quick release of the hostages, a handover of occupied government buildings and stressed the importance of holding Ukraine's presidential vote as planned on May 25.

Steinmeier's trip is part of the road map for settling Ukraine's crisis laid out by the Organization for Security and Co-operation in Europe, a top trans-Atlantic security and rights group. Russia, which is an OSCE member, has welcomed its efforts to mediate the crisis.

Russia's Foreign Ministry on Tuesday assailed what it called the Ukrainian authorities' reluctance to talk with pro-Russia insurgents, saying "it poses a serious obstacle on the path of de-escalation." Russia urged the United States and the European Union to persuade authorities in Kyiv to prioritize discussions of giving more powers to Ukraine's regions ahead of the May 25 presidential vote.

The separatists held a referendum Sunday and claimed that about 90 per cent of those who voted in Donetsk and Luhansk backed sovereignty. The two regions declared independence on Monday and insurgents in Donetsk even asked to join Russia.

Moscow pushes talks

Ukraine's acting president called the vote a sham and Western governments said it violated international law.

The Kremlin has shown no immediate intentions of annexing eastern Ukraine the way it did the Crimean Peninsula in March. Instead, Moscow has pushed for talks between Ukraine's central government and eastern regions on Ukraine's future — a cautious stance suggesting that Russia prefers a political rather than a military solution to its worst standoff with the West since the Cold War.

The Ukrainian government and the West have accused Russia of fomenting the mutiny in the east to derail Ukraine's presidential vote and possibly grab more land. The insurgents in Luhansk said they wouldn't hold the presidential vote.

The OSCE plan presented Monday by Swiss President Didier Burkhalter calls on all sides to refrain from violence and urges immediate amnesty for those involved in the unrest, talks on decentralization and the status of the Russian language. Burkhalter said the OSCE will set up rapid response teams to quickly investigate all acts of violence.

More powers

He said the plan envisages a quick launch of high-level round tables across the country bringing together national lawmakers and representatives of the central government and the regions.

Serhiy Taruta, the Kyiv-appointed governor of the Donetsk region, on Tuesday urged the Ukrainian parliament to authorize a referendum on June 15 that could help the regions gain more powers while remaining part of Ukraine.

While he dismissed the vote held by pro-Russian protesters on Sunday as an "opinion poll," Taruta said everyone in Ukraine, including those in the rebellious east, "should hear answers to the questions that they are concerned about."

Taruta said key issues include possibly devolving more powers to local authorities, creating municipal police forces and a broader use of languages other than Ukrainian.

The interim government in Kyiv had been hoping the May 25 presidential vote would unify the country behind a new, democratically chosen leadership. Ukraine's crisis could grow even worse if regions start rejecting the presidential election. Dozens of people have been killed since Ukrainian forces began trying to retake some eastern cities from the separatists.

On Tuesday, insurgents said unidentified assailants fired at a car carrying Valery Bolotov, a separatist leader in the Luhansk region. Bolotov was hospitalized with wounds but they were not life-threatening, the insurgents said. Bolotov was the one who announced independence Monday for his region.