Macedonia declared a state of emergency in its capital Skopje and neighboring districts on Sunday, a day after at least 21 people were killed in flash floods caused by a storm.
Torrential rains flooded homes, swept away a section of the ring road around Skopje and wrecked cars late on Saturday evening. Northern suburbs of the capital were particularly hard hit, though the city center also suffered flash floods.
Children were among those killed, a police spokesman said, adding that searches were continuing for six people who have been reported missing.
Macedonia, a small former Yugoslav republic of about two million people, has declared Monday a day of national mourning.
"This is a catastrophe of unprecedented magnitude," Deputy Prime Minister Nikola Todorov told reporters.
People walk on the street after heavy floods in Cento near Skopje, Macedonia, August 7, 2016.
Special police forces and trucks loaded with drinking water were sent to the worst affected areas, where there also have been some electricity outages and where scattered debris of furniture swept away from houses could be seen on the streets, a Reuters reporter said.
The rain had stopped by Sunday morning and water levels were receding, though there was some more rain on Sunday evening in Skopje. There were no reports of further flash flooding.
European Union Enlargement Commissioner Johannes Hahn said on Twitter that the EU stood ready to help Macedonia, which is a candidate to join the bloc.
Further north in the Balkans, in Croatia, heavy winds caused disruptions on some roads, including the closure of the highway linking the capital Zagreb to southern coast for lorries and buses, local media said.