A helicopter was flying over the area, monitoring the situation. Serbian police officers were also dispatched to the border to control the situation.
Hungarian authorities began procedures to close the one remaining border crossing along the 109-mile barbed-wire-fenced southern border on Monday afternoon.
Tighter border control laws in Hungary, which criminalize illegal border crossings, are expected to come into force on Tuesday.
Budapest estimates that some 172,000 refugees and migrants have entered the country since the beginning of 2015.