In Zittau, on Germany's eastern fringe — where the country meets Poland and the Czech Republic — Chancellor Angela Merkel, Polish Prime Minister Donald Tusk and European Commission President Jose Manuel Barroso raised a border gate as children set loose dozens of blue balloons covered by stars — symbolizing the EU flag. "We are all quite happy to be able to celebrate this truly historic moment together," - Merkel said.

Poland, Hungary, the Czech Republic, Slovakia, Slovenia, Estonia, Latvia, Lithuania and Malta joined the EU in 2004, but could not be part of the Schengen frontier-free zone until now because their police and border guards were not considered in line with EU norms.

"It would have been better to wait a year or two longer to abolish the border controls," said Joachim Herrmann, the interior minister of the German state of Bavaria, which borders the Czech Republic.

Bulgaria's Foreign Minister Ivailo Kalfin said Friday his country will be ready to join the Schengen zone by 2011. "It depends, of course, on how prepared Romania will be, since it would be strange for Bulgaria to join, but to have a Schengen border with Romania." - Kalfin said

On the Polish side, in Porajow, Tusk said the day was "exceptional" for the Poles, Germans and Czechs who came of age in a divided Europe.

Hours before the controls ended at midnight Thursday, Polish and German officials gathered at the Frankfurt an der Oder border crossing, east of Berlin, cutting a symbolic ribbon.

But the move has also forced the EU to tighten controls on its new eastern borders to prevent infiltration by criminal gangs, illegal immigrants and even terrorists.

The EU's front line in the fight against illegal immigration remains to the south where thousands of poor Africans make a hazardous sea journey to the coasts of Spain, Italy, Malta and Greece, while would-be migrants from the Middle East and Asia take the overland route through Turkey and the Balkans.

Austrian Chancellor Alfred Gusenbauer dismissed concerns that the expansion would aid criminals or illegal immigrants as he symbolically joined Slovakia's Prime Minister Robert Fico to saw through a barrier on the countries' border. "Schengen is not crime, not insecurity, not fear," Gusenbauer said. "Schengen stands for freedom, security and stability."

The Schengen agreement is named after the village in Luxembourg where it was signed in 1985 by France, Germany, Belgium, Luxembourg and the Netherlands to allow citizens to travel freely between them. Since then, they have been joined by Italy, Spain, Portugal, Greece, Austria, Denmark, Sweden and Finland, as well as non-EU nations Norway and Iceland.

Beginning Friday, Serbian citizens need the EU's Schengen visas to travel to neighboring Hungary, or even to Slovenia — the country they shared the old six-republics Yugoslav federation with until 1991.

Serbia's pro-Western officials hope that Serbia could by 2009 be placed on the so-called "white Schengen list" that would allow its citizens to travel visa-free.

But because of its perennial political instability, and fears that Serbs would flee en masse to the West if the visas were lifted, the EU has kept the requirement — although some categories, such as students, researchers, business people and journalists will be able to obtain visas to the EU more quickly as of Jan. 1.