EU states on Thursday cleared Bulgaria and Romania to become full members of the borderless Schengen zone from the start of next year, officials said. 

"It is a historic moment to finally welcome Bulgaria and Romania," said Hungarian Interior Minister Sandor Pinter, whose country holds the EU's rotating presidency.

The two countries, both members of the European Union since 2007, were partially integrated into the free movement zone in March, opening up travel by air and sea without border checks.

But Austria held up their full entry over migration concerns, which meant that controls still applied at their land routes. 

Vienna announced Monday that it would not use its veto at Thursday's meeting of EU ministers, paving the way for the two to become full members from January 1, 2025. 

Bucharest and Sofia fulfilled all technical criteria set out by Brussels in 2010, but spent more than a decade waiting to join the Schengen zone as various member states blocked their entry.

Since 2022, their applications have been held up by Austria, which had for years complained about hosting a disproportionate number of undocumented immigrants as a result of poorly protected external Schengen borders.

Austria dropped its objections after the three countries signed a "border protection package" agreement in Budapest.

The agreement foresees the joint deployment of border guards to the Bulgarian-Turkish border and temporary border controls on land routes for an initial period of six months, according to Austrian Interior Minister Gerhard Karner.

Created in 1985, the Schengen zone currently comprises 29 members - 25 of the 27 European Union member states as well as Switzerland, Norway, Iceland and Liechtenstein. 

It is the world's biggest area without internal border controls, where more than 400 million people can travel freely inside the zone.