Germany's Angela Merkel welcomed French President Francois Hollande to a picturesque Baltic coastal town Friday for talks meant to strengthen the personal chemistry between the two leaders at the heart of Europe.

Braving a slight drizzle, Merkel greeted Hollande in the seaside resort of Sassnitz, saying that getting to know each others' homes, "in view of the many problems we have to discuss, is a good thing."

The flag of the self-proclaimed Donetsk People's Republic flew in Riga Friday in a show of support from Latvia's large Russian minority for pro-Moscow separatists in Ukraine.

"It is unfortunate that there are people trying to mar a commemorative event with such provocations," Latvian foreign ministry spokesman Karlis Eihenbaums told Agence France Presse.

Russia's deputy prime minister visited Moldova's breakaway Russian-speaking region of Transdniestr on Friday in the most senior visit since the start of the crisis in neighboring Ukraine.

Deputy Prime Minister Dmitry Rogozin vowed support and protection from Ukraine as he visited and watched a military parade in the city of Tiraspol in an apparent endorsement of pro-Russian separatists there.

Pro-Russian rebels fighting in eastern Ukraine on Friday tapped a man authorities in Kiev suspect is a colonel in the Russian security services to lead their insurgency.

Igor Strelkov, currently heading the militants in the flashpoint city of Slavyansk, has been "put forward" to become "the commander of all self-defense forces in (the region of) Donbass," said the self-proclaimed governor of Donetsk, Pavlo Gubarev.

Germany's Angela Merkel from Friday will host French President Francois Hollande in a picturesque Baltic coastal town for informal talks meant to strengthen the personal chemistry between the two European leaders.

A range of pressing issues -- including the tense standoff with Moscow over Ukraine, European elections in two weeks and a possible major trans-border corporate deal -- will be on the agenda of the two-day visit starting 1400 GMT on what is the EU's official "Europe Day".

Fierce fighting between Ukrainian troops and pro-Russian rebels broke out in the southeastern city of Mariupol on Friday, killing 21 people, all but one of them insurgents, Ukraine's interior minister said.

An attempt by around 60 rebels armed with automatic weapons to storm the police headquarters turned into a "full-scale military clash" when army and interior ministry troop reinforcements arrived, Arsen Avakov said on his official Facebook page.

President Vladimir Putin reviewed Russian ships in the port of Sevastopol on Friday as he visited Russia's naval base in the Crimean port for the first time since Moscow's annexation of the Black Sea peninsula.

Russian television showed live footage of Putin standing on a white vessel passing at least 10 navy ships in the port, stopping at each to congratulate the sailors for Victory Day, Russia's celebration of the defeat of Nazi Germany.

The spiritual leader of Crimea's Tatars appealed to the international community Thursday not to forget the Black Sea peninsula, annexed by Russia, as attention has turned to growing violence in eastern Ukraine.

"We are concerned that because of Russia's recent actions, the issue of Russia's occupation of Crimea has become secondary in light of the potential threat of Russian forces invading across the eastern border of Ukraine," Mustafa Dzhemilev, spiritual leader of the ethnic Tatar community in Crimea, said in Vienna.

A U.S. warship arrived on Thursday in Georgia's port of Batumi, the U.S. embassy said, sending a message of support to NATO allies amid the spiraling crisis in neighboring Ukraine.

The USS Taylor's "presence in Georgia reaffirms the United States' commitment to strengthening ties with NATO allies and partners like Georgia, while working toward mutual goals of promoting peace and stability in the region," the embassy said in a statement.

Russian President Vladimir Putin will attend ceremonies in France next month marking the 70th anniversary of D-Day despite the Ukraine crisis, the ambassador to Paris said Thursday.

"President Putin has been invited by President (Francois) Hollande to take part in the ceremonies to commemorate the Normandy landings on June 6. He has accepted the invitation. He will be coming on June 6," Alexander Orlov told BFM television.