French Foreign Minister Laurent Fabius has ruled out going to war with Russia over Ukraine, but warned more sanctions will be leveled against Moscow if it tries to undermine the May 25 presidential vote.

"We cannot accept the annexation or the fact that Ukraine would be controlled or invaded," Fabius, who visits the United States this week, said in an interview published Sunday in The Washington Post.

As thousands turned out Sunday for rebel-held independence "referendums" across swathes of eastern Ukraine, the small town of Svatove stood out as a brave refusnik -- apparently the only one in the voting region.

In this town of some 20,000 inhabitants, the Ukrainian flag still flutters proudly over the town hall, in contrast to the dozen towns and cities in eastern Ukraine that have been overrun by pro-Russian rebels.

Russia's interest in Ukraine is for "short-term gain," and its troops remain massed along the Ukrainian border, U.S. Pentagon chief Chuck Hagel said in an interview that aired Sunday.

Speaking on ABC's "This Week" Hagel qualified Russia as an "adversary in Ukraine," but stopped short of calling it an enemy.

Russia's deputy prime minister said Sunday he had managed to bring to Moscow boxes of petitions asking Russia to recognize Moldova's breakaway Transdniestr region despite an attempt by authorities in Chisinau to confiscate them.

Transdniestr, which borders Ukraine and is mainly Russian-speaking, declared independence from Moldova in 1990 and has Russian troops stationed there but is not recognized by any country.

French President Francois Hollande starts a three-day visit to the South Caucasus on Sunday as he seeks to bolster European ties on Russia's southern doorstep amid the crisis in Ukraine.

Hollande was due to arrive in the Azerbaijani capital Baku around 6:00 pm (1300 GMT) Sunday, on the same day separatists in eastern Ukraine held referendums on breaking away from the country.

Pro-Russian rebels claimed a massive turnout in a vote they held Sunday to split east Ukraine into two independent republics, though Kiev slammed it as a "farce" amid Western fears it could lead to civil war.

Thousands of people queued in front of a limited number of polling stations in the restive provinces of Donetsk and Lugansk to cast their ballots, Agence France Presse journalists in several towns reported.

Lithuanians began voting Sunday to elect their president, with incumbent "Iron Lady" Dalia Grybauskaite an apparent shoo-in as fears in the EU Baltic state soar over a resurgent Russia.

The karate black belt, nicknamed for her Thatcheresque resolve, is poised to win a second term as many here who remember Soviet times see her as a their best hope amid Europe's worst standoff with Moscow since the Cold War.

The Red Cross Saturday called on all sides in the Ukraine crisis to respect the neutrality of its members after nine aid workers were held for hours in the eastern city of Donetsk.

The International Committee of the Red Cross "is a neutral, impartial and independent humanitarian organisation," Michel Masson, the head of the ICRC delegation in Ukraine, said in a statement.

France and Germany Saturday threatened Russia with "consequences" if Moscow disrupts Ukrainian presidential elections later this month, stepping up diplomatic pressure on the eve of "illegal" referendums the West fears will split the country apart.

In a joint statement, French President Francois Hollande and German Chancellor Angela Merkel also urged Ukraine's security forces to stop their offensive on rebel-held positions in the run-up to the planned May 25 presidential part.

Several Red Cross members whom rebels said they had detained in the eastern Ukrainian city of Donetsk have been released, an official from the organization in Kiev told Agence France Presse Saturday.

"An emergency response team from the local Red Cross and one member of the international Red Cross were detained. They are now all free," said the official, who did not wish to be named.