He said a European Union leaders' meeting in Brussels failed to decide on a common force to protect Greece's borders and that it was clear that Hungary had to protect the external frontiers of the EU's passport-free Schengen zone.
"Therefore, the national security cabinet decided that from midnight ... Hungary will fully enforce the Schengen rules on the border with Croatia," he told reporters after the cabinet meeting. Official border crossings will continue to work, but with stricter control, he added.
He said Hungary had informed Croatia, Slovenia, Poland, Slovakia, Austria, and Germany about the decision to seal the border. He said migrants would be able to submit asylum requests at two transit zones to be set up on the border with Croatia, and crossing will only be possible via official border stations.
Janos Lazar, Prime Minister Viktor Orban's chief of staff, said on Thursday that Hungary's fence on the border with Croatia was ready and that the army and the police could seal off the border as soon as such a decision was made.
More than 378,000 migrants have transited through Hungary, he told journalists, estimating that a total of 600,000 to 700,000 people could reach Hungary's border by the year's end.
Since September 16, 185,300 migrants have entered Croatia, including 5,138 on Thursday and 4,193 from midnight to 3 pm on Friday, the Interior Ministry said.
Slovenian PM Miro Cerar said after the Brussels meeting that Slovenia would have to take appropriate measures if Hungary closed its border with Croatia, which would cause migrants to start heading for Slovenia. He said Slovenia was preparing for that but that it did not want such unilateral moves. He said he had informed Orban of this on the fringes of the meeting and that he had discussed the matter with Croatian PM Zoran Milanovic and Austrian Chancellor Werner Faymann too.
Cerar convened the National Security Council for Saturday in connection with the refugee crisis after Hungary's decision to close its border with Croatia, Slovenian Radio said.