German Chancellor Angela Merkel has said the discovery of at least 20 dead migrants in a truck in Austria is a warning to Europe to get to grips with the migrant crisis.
Speaking in Vienna, where leaders from the EU and Western Balkans are meeting for a summit focusing on migration, Merkel said, "This reminds us that we must tackle quickly the issue of immigration and in a European spirit -- that means in a spirit of solidarity -- and to find solutions."
She also said Western Balkan countries are facing "huge challenges" handling tens of thousands of migrants from conflict-hit states in the Middle East and Africa trying to get to the EU.
Austrian police said there appeared to be at least 20 partially decomposed bodies in the lorry parked near the Hungarian border.
Police officials said the truck had Hungarian license plates.
Police said the state of the bodies made establishing the identity and exact number of dead migrants difficult, but the total number could rise to 50.
The truck was apparently abandoned on August 26 and its back door was left open.
Interior Minister Johanna Mikl-Leitner condemned the traffickers.
"Human smugglers are criminals," she said in a statement. "Those who still think that they are gentle helpers of refugees are beyond saving."