Serbian police said they have detained six people for smuggling 78 migrants trying to reach the European Union on July 19.
Police said they discovered the migrants in two separate incidents near the Bulgarian border -- 37 migrants from Afghanistan and Pakistan were hidden in a van intercepted on a regional road, while another 41 people from Syria were caught crossing illegally from Bulgaria.
The arrests came as Bulgaria announced it had detained 45 migrants who were trying to cross into Serbia, including 30 Afghans, 13 Pakistanis, and two Iranians.
Serbia has been stepping up efforts to stop the migrant influx, including forming joint police and army teams that will patrol the borders with Bulgaria and Macedonia. The country wants to avoid a migrant pileup after EU member Hungary recently introduced tough antimigrant measures.
The Serbian army commander, General Ljubisa Dikovic, and senior police official Vladimir Rebic jointly toured the border area with Bulgaria on July 19, the Defense Ministry said.
It said joint forces are "currently being formed" but didn't specify when they will take up positions. An army general will be in charge.
Based on reporting by AP and Reuters