The European Union formally ramped up its Frontex border agency on Thursday, giving it more powers to control migrant flows and protect the bloc's external frontiers following a surge last year in arrivals.
Border controls have been a jealously guarded national competence in the 28-country EU, but some member states struggled to contain last year's flow of more than 1 million migrants and asylum seekers entering Europe.
The agency, rebranded as the European Border and Coast Guard, will stress-test external EU borders to spot weaknesses and set deadlines for member states to address any shortcomings.
As a last resort, countries within the border-free Schengen zone will be able to reintroduce border controls if a member state does not cooperate.
The agency will also have access to a rapid reserve pool of 1,500 border guards and technical equipment to help states deal with high migration pressures or other emergencies - assistance that it will also be able to provide to countries neighbouring the EU.
"The new agency is stronger and better equipped to tackle migration and security challenges at Europe's external borders," said its chief, Fabrice Leggeri. It will also play a greater role in returning migrants who have no right to stay in the EU.
The agency's new powers will be rolled out in the coming months, with it set to expand its budget and more than double in manpower by 2020. The first assessments of external EU borders are due to be completed in the first months of 2017.
EU Migration Commissioner Dimitris Avramopoulos described the launch as a "milestone" in EU border management, in a ceremony held on the Bulgarian-Turkish border.
"The door is open for the ones who are in need of international protection and closed to the ones who want to cross our borders illegally," he added.
Bulgarian Prime Minister Boyko Borisov, meanwhile, stressed the importance of Ankara as a strategic partner in managing migration flows.
Most migrants and asylum seekers reached Europe last year by taking boats from Turkey to Greece. That route was largely shut off earlier this year, placing the spotlight on Bulgaria, which shares a 259-kilometre land border with Turkey.
Sofia is currently extending a fence along that frontier aimed at keeping out illegal border crossers, and this week received just over half of a 108-million-euro (121-million-dollar) European Commission contribution to help tackle migration.