As many as 45 migrants have been detained trying to cross into Serbia from Bulgaria, officials from the latter country say.
Of these, 30 are Afghan nationals, 13 are from Pakistan, and two from Iran, according to border police.
They did not try to cross the border together but were caught doing so in several groups.
Some of those detained had “registration cards issued by the State Agency for Refugees”, according to a police statement which does not elaborate whether the people in questions had been granted status.
Earlier, Serbia announced it would set up a joint army and police force to patrol across the borders with Bulgaria and Macedonia, arguing lax controls were resulting in an inflow of Middle Eastern migrants into its territory.
That followed moves by Hungary to announce it would begin sending thousands of migrants back to Serbia.
Sofia, however, claims Belgrade has no reason to worry of an increased migratory pressure on the border with Bulgaria.