BELGRADE (Reuters) - Serbian authorities have detained 20 migrants in the north of the country while up to another 200 were rounded up and sent to a camp in the south, a government official said on Tuesday.

“Twenty people have been taken in for questioning,” the official who asked not to be named told Reuters without elaborating further.

He added the other migrants were taken away from in and around Sid in three buses to a camp in Presevo, near the Macedonian border in the south.

The police action in the northern town of Sid, which is only a few kilometres from EU member Croatia’s border, was launched after municipal authorities complained about incidents involving the migrants, local Sremska TV reported on Tuesday.

The so-called Balkan route for migrants trying to reach western Europe was shut last year when Turkey agreed to stop the flow in return for EU aid and a promise of visa-free travel for its own citizens.

But people mainly from the Middle East, Africa and Asia continued to arrive to Serbia, mainly from Turkey, via neighboring Bulgaria.

After Hungary began reinforcing its second border fence with Serbia earlier this year to deter migrants, asylum seekers are now attempting to enter the EU across the less protected border between Serbia and Croatia.

Rados Djurovic, the executive director of Asylum Protection Centre, said the tensions between locals and migrants were on the rise.

“We now have both local population and migrants that are nervous and exhausted ... this will become more pronounced as the crisis continues,” Djurovic said.

Last year Serbia deployed joint military and police patrols to patrol its borders between Bulgaria and Macedonia. There are over 8,000 migrants in Serbia.