The central European country installed the border controls on Oct. 5, following neighbours Poland, the Czech Republic and Austria, which had tightened their own frontiers with Slovakia.
Slovakia saw a more than 500% year-on-year increase in the number of illegal migrants detained between the start of 2023 and Nov. 12, according to a statement accompanying the measure that was approved by the government on Monday.
Detentions, though, have dropped to 29 in the week to Nov. 12, from 1,690 in the first calendar week after controls began.
"It can be concluded the controls on internal borders, along with similar measures in neighbouring states, have a preventive character," the Interior Ministry said in the statement.
Slovak Prime Minister Robert Fico returned to power for a fourth time last month after winning a September election in which his pledges to protect borders from illegal migration played a role in campaigning.
Migrants, predominantly young men from the Middle East and Afghanistan, have mostly come via the so-called Balkan corridor, through Hungary from Serbia, heading to wealthier Germany and other western European countries.
Slovakia, the Czech Republic, Poland, Hungary, Austria and Germany - which have all deployed border measures in recent months - are part of the European Union's Schengen open-border zone.
(Reporting by Jason Hovet in Prague; Editing by Emelia Sithole-Matarise)
