BRATISLAVA, Slovakia - Slovak banks did brisk business as they opened on New Year's Day for a very special occasion -- issuing euros to citizens eager to get their hands on the country's new currency.

The small alpine state of 5.4 million people on Thursday became the 16th country to adopt the euro.

The European Union currency also celebrated its 10th birthday this New Year's Day.

With the addition of Slovakia, the euro will now be used by 330 million people with an annual gross domestic product of more than four trillion euros or some US$5.6 trillion.

The decision by Slovakia to join the eurozone and abandon the Slovak koruna appears even wiser now amid the global financial crisis.

Many other European countries that have not made the switch have seen their currencies severely buffeted in the current downturn.

"I congratulate Slovakia and warmly welcome all its citizens to the euro area," said EU Commission President Jose Manuel Barroso. "The euro will help Slovakia to take part in, and benefit from, Europe's collective effort to recover from the current economic crisis.

"But the euro is more than just money. On this historic New Year's Day, Slovakia is a powerful symbol of economic and political progress and of European integration."

Slovak Prime Minister Robert Fico's comments were tinged with nostalgia.

"We're saying goodbye to the Slovak currency that meant so much to us," he said. "Part of us, the Slovak identity, is leaving."

Still, Fico was among the first Slovaks to slip the new bills into his wallet, pulling five crisp, 20-euro notes out of an automated teller machine set up at Slovak parliament shortly after midnight.

Slovakia is adapting as some people in EU members Denmark and Sweden are rethinking their countries' refusal to sign up. Czech Prime Minister Mirek Topolanek said Thursday his government will set a target date for the euro's adoption in November.

Other countries have seen their currencies hit badly. Neighbouring EU member Hungary, once the beacon of economic success in post-communist Eastern Europe, was forced earlier this year to accept a bailout from the International Monetary Fund to avert economic collapse, as has non-EU member Ukraine.

Iceland, neither an EU nor a euro member, has suffered badly as an outsider, being hit with a combination of a plunging currency and the popularity of high-interest foreign currency loans. That means monthly loan repayments for cars and homes have doubled this year, jolting Icelanders as the economy teeters and jobs are slashed.

Katinka Barysch, an analyst at the London-based Centre for European Reform think-tank, said recent currency swings have underlined the benefits of the euro to Eastern European states.

"The very stark experience of being in the middle of a global economic storm means they have felt very cold and uncomfortable," she said.

Slovakia is also the first country that used to be in the Soviet orbit to join the eurozone -- while Slovenia also was communist ruled, it was part of Yugoslavia, which kept its distance from Moscow.

The euro was introduced on financial markets on Jan. 1, 1999, and notes and coins first came into circulation in 2002. The zone widened to 15 countries in January 2008 when Cyprus and Malta joined; the other members are: Belgium, Germany, Ireland, Greece, Spain, France, Italy, Luxembourg, the Netherlands, Austria, Portugal, Slovenia and Finland.

Slovakia's old currency will be in circulation alongside the euro until Jan. 16. Banks also planned to open over the weekend to aid the transition.