Syria's Kurds reacted coolly Friday to the prospect of hundreds of rebel fighters joining their defense of the border town of Kobane, suggesting they should focus on fighting jihadists elsewhere.

Turkey said on Friday that 1,300 Free Syrian Army (FSA) fighters -- who are battling to oust Syrian President Bashar al-Assad -- would travel to Kobane, located just across its border.

Nordic and Baltic foreign ministers on Friday demanded Russia immediately free an Estonian policeman charged with espionage in a case that has heightened tensions between Estonia and its Soviet-era master. 

Russia's arrest of an Estonian policeman has sparked fears that Moscow is using the incident to test NATO's resolve to defend its small Baltic allies as the crisis in eastern Ukraine rumbles on.

U.S. President Barack Obama will go to Estonia next month to reaffirm Washington's commitment to NATO allies at a time of rising tensions with Russia over Ukraine, the White House announced Friday.

"In light of recent developments in Ukraine, the United States has taken steps to reassure allies in Central and Eastern Europe, and this trip is a chance to reaffirm our ironclad commitment to Article V as the foundation of NATO," the White House said.

Living with sub-zero temperatures for several months a year, Estonians are no strangers to a little snow.

But residents of the Baltic nation were baffled on Tuesday when flurries of the white stuff fell in June for the first time in more than three decades.

Four Danish F-16 warplanes landed in Estonia on Wednesday, marking the first time NATO planes will be stationed in the ex-Soviet state and Russian neighbor. 

The aircraft and a supporting team of 60 people arrived at the Amari air base in the west of the Baltic state at a time when NATO is reinforcing its presence in the region to allay concerns triggered by the Ukraine crisis.

Estonia's new Prime Minister Taavi Roivas became the European Union's youngest head of government on Wednesday after parliament swore in his new bi-partisan cabinet.

Roivas, 34, has brought together his center-right Reform Party with the leftist Social Democrats, who crossed over from the opposition ahead of a general election next spring.

Estonia's president on Friday designated 34-year-old Taavi Roivas as the eurozone member's prime minister, paving the way for him to become the youngest head of government in the European Union.

"I expect the new government to show a stronger interest in social issues and a willingness to listen to all sides," President Toomas Hendrik Ilves told reporters.

"Putin = Dracula," "Putin = Hitler," "Putin, get out": posters and caricatures attacking the Russian leader have multiplied over the last couple of weeks on the Maidan, Kiev's protest tent-city.

As Russian forces have taken control of Ukraine's Crimean peninsula, protesters have reveled in making comparisons between Russian President Vladimir Putin and Adolf Hitler, combining their names in slogans that conclude that "Putler has gone mad."

Europeans have overreacted to allegations that the United States had been snooping on them and vacuuming up huge amounts of phone and Internet data, cyber-savvy Estonia said in an interview published Thursday.

"I could understand such condemnation from European countries that are lily white virgins and not themselves involved in these kinds of activities," Estonian President Toomas Hendrik Ilves told Estonia's leading Postimees daily.