Ukraine on Thursday reported the death of five soldiers while pro-Russian rebels accused government troops of killing a civilian in clashes following failed talks on ending a 16-month conflict in the country's east.

Military spokesman Oleksandr Motuzyanyk told reporters in Kiev that six servicemen had also been wounded in the past 24 hours of fighting across the eastern Russian-speaking provinces of Lugansk and Donetsk.

France's defense minister said on Thursday that "several" countries had expressed an interest in buying its Mistral-class warships, after Paris refused to deliver them to Russia because of the Ukraine crisis.

"A certain number of countries -- there are several -- have made their interest known for these boats," Jean-Yves Le Drian told RTL radio.

Ukraine's security service said on Wednesday it had seized a small quantity of what appeared to be non-fissile uranium in a peaceful western region of the war-torn former Soviet state.

The State Security Service of Ukraine (SBU) said a group of criminals had been trying to sell the uranium-238 isotope -- common in nature and often found in phosphate fertilizers -- to an unknown client at the time of their arrest.

Ukrainian President Petro Poroshenko convened his top generals Tuesday to discuss the latest failed peace talks with pro-Russian militias, aimed at stemming clashes that saw seven troops killed in another wave of attacks.

Poroshenko has found himself trapped between Ukrainian nationalists who fear losing land to the eastern pro-Russian fighters, and Western pressure to resolve the 15-month crisis in the European Union's backyard.

An exiled former top ally of ousted Ukrainian leader Viktor Yanukovych on Monday launched a shadowy committee to "save" the war-torn country, pledging to bring down the current pro-Western government.

Ex-prime minister Mykola Azarov, wanted for corruption by Kiev after fleeing during last year's protests that toppled Yanukovych, called for public demonstrations and early elections in Ukraine at a press conference in a Moscow hotel.

Ukraine on Monday reported the death of four soldiers in widespread clashes with pro-Russian rebels that came only hours ahead of fresh talks on ending the 15-month separatist revolt.

Military spokesman Andriy Lysenko said another 15 servicemen had been wounded in the past 24 hours of fighting across the eastern Russian-speaking provinces of Lugansk and Donetsk.

Russian President Vladimir Putin is having a change of heart on the Kremlin's wholehearted support for Syrian leader Bashar Assad and may "give up on him" in the future, Turkish President Recep Tayyip Erdogan was quoted as saying Monday.

When asked if Putin could be persuaded not to support Assad, Erdogan said he saw his counterpart as "more positive" during a face-to-face meeting in the Azerbaijani capital of Baku in June and in subsequent telephone talks. 

Ukrainian President Petro Poroshenko on Monday accused his Russian counterpart Vladimir Putin of wanting to take over the "whole of Europe" and potentially aiming his sights next at Finland and the Baltics.

"Putin wants to go as far as we allow him -- not only Ukraine, but the whole of Europe," Poroshenko said in an interview with French radio station RFI. 

Ukraine's highest court on Friday allowed parliament to vote on Western-backed constitutional amendments aimed at stemming daily bloodshed by giving pro-Russian insurgents partial autonomy in the separatist east.

The idea of granting at least three years of self-rule to rebellious parts of Ukraine's industrial war zone has struck a note of disquiet among many lawmakers and much of the Kiev media.

Finland has asked the United States to explain why two Finnish citizens and four enterprises have been slapped with sanctions over the conflict in Ukraine, the Finnish Foreign Ministry said on Friday.

"When we were informed of this, we asked the U.S. authorities for the grounds of these sanctions. In the global economy this has negative implications for those listed," the ministry's head of legal services, Paivi Kaukoranta, told AFP.