Authorities in the Balkan countries say people have been collapsing on the streets amid a heat wave that have seen temperatures in the region reach 40 Celsius (104 Fahrenheit).

The high temperatures began to rise over the weekend and peaked on Monday. No casualties were reported but authorities said hundreds of people were treated for dehydration in Bosnia, Romania, Croatia, Serbia, Montenegro and Hungary.

Southern Bosnia was also hit by several forest fires, including one near the small village Medjugorje, which is a popular Catholic pilgrimage site.

Public swimming pools in the Hungarian capital Budapest have extended their working hours into the night and water trucks have been spraying tram tracks to prevent them from warping.

In Belgrade, authorities parked trucks with water tanks throughout the city.