Railway services across Serbia were suspended on Saturday ahead of a major student protest in Belgrade.
A short statement published on the website of operator Srbija Voz at 4:15 am (0215 GMT) said services would be halted "for the time being" nationwide.
The company did not give a reason for the suspension.
A railway employee at a ticket counter in the northern border city of Subotica was also unable to give a reason for the suspension when asked by a dpa reporter.
The government has suspended railway services twice in the past ahead of student protests, which are part of a broad movement that emerged following the collapse of a railway canopy in the city of Novi Sad in November 2024 that left 16 dead.
Serbia's university students have been at the forefront of protesters calling on President Aleksandar Vučić to resign over the tragedy, accusing the government of negligence and corruption.
The government responded to the protests with a harsh crackdown on demonstrators and arbitrary arrests of organizers and supporters.
On the two occasions in March and June last year, authorities cited "anonymous bomb threats," while observers believed that the move aimed to keep protesters from outside Belgrade to join rallies in the capital, which drew tens of thousands of people.
Organizers are expecting similar numbers at the protest on Belgrade's Slavija Square on Saturday evening.
