Airports in Sofia and Bucharest on Sunday removed passport check points for those departing to or arriving from most European Union member states as Bulgaria and Romania partially joined the Schengen open-travel zone.

The two countries reached an agreement late last year to join Europe's free-travel area by air and sea after Austria opposed full membership, including land crossings, saying Romania and Bulgaria needed to do more to prevent illegal immigration.

"Of course this is a very beautiful achievement for Bulgaria which makes things easier for us, as Bulgarians," said Mincho Yurukov, who arrived to Sofia airport from Berlin.

"Also, we feel like Europeans, that is a very important thing, the flight is much nicer, no checks."

The Interior minister in the outgoing government, Kalin Stoyanov, told journalists on Sunday that Bulgaria should become a full member of the Schengen zone by the end of this year, meaning border check points will be removed for people and goods travelling by road and by rail.

The Romanian prime minister has also said the country expects to finish negotiations on land borders this year.

"I welcome the lifting of internal air and sea border checks. This is a great success for both countries," European Commission President Ursula von der Leyen in a statement.

"Together, we are building a stronger, more united Europe for all our citizens,” she said.

Bulgaria and Romania have joined a regional police initiative with Austria, Greece and Slovakia to counter the flow of migrants.

The European Union's border agency Frontex said last month it would triple the number of its officers in Bulgaria to help stem the amount of people crossing into the bloc from Turkey.

(Reporting by Stoyan Nenov; Writing by Ivana Sekularac; Editing by Kirsten Donovan)