Bulgaria is to deploy more than 400 troops and other security personnel to boost security on its southern border.
"Hundreds of people, more than 400, from the army, paramilitary police and police, will stay here permanently," said Prime Minister Boiko Borissov on Saturday at the Greek border near Macedonia.
Another 500 security personnel could be mobilized within hours if necessary, he said.
Bulgaria already has close to 2,000 border police officers guarding its porous 260-kilometer (160-mile) frontier with Turkey.
Last month, Bulgaria's parliament agreed to give the army greater powers to beef up security on the borders against a possible increase in the flow of refugees passing through to the north as the weather gets warmer.
Bulgaria, which is one of the poorest member states of the European Union, is currently extending a 30-kilometer razor-wire fence to better fend off refugees.
Bulgarian police are notorious for their harsh treatment of refugees, and so far the country has not been on the list of the main routes used by refugees on their way to northern Europe.
The Bulgaria-Greece border is mountainous and deemed mostly impassable for poorly equipped refugees fleeing from war and poverty in Syria, Iraq, Afghanistan and elsewhere in the Middle East and North Africa.
The European Commission’s bureau of statistics, Eurostat, said in a report on Friday that some 1,255,600 refugees reached the EU zone in 2015.
Many blame Western intervention in conflicts in the Middle East as the main reason behind the departure of refugees from their home countries.