Huge traffic queues have formed on a Hungarian motorway leading to Austria after border controls were tightened in a bid to clamp down on human trafficking.
Austrian officials put tougher checks in place on the country's eastern border after the bodies of 71 migrants were found in the back of a lorry abandoned on a motorway.
Five people have been arrested in connection with the incident.
Angela Merkel has said the discovery of up to 50 refugees found dead in a parked lorry in eastern Austria, close to the Hungarian border, has "shaken" European leaders attending a summit in the Balkans.
The Austrian Interior Minister Johann Mikl-Leitner said it was "a dark day" and reiterated the country's demand that the EU find a way to distribute refugees fairly among the member states.
"This is a signal on the European level to act as quickly as possible", she told a news conference.
Police made the discovery in a 7.5 tonne lorry stopped on the A4 motorway near the town of Parndorf. The exact number of victims is not yet confirmed.
The truck is said to have Hungarian number plates and investigations are underway to discover the circumstances around the deaths.
Tens of thousands of people, mainly from Africa and the Middle East, have made the dangerous crossing to Europe with those who make it ashore attempting to make their way north via the Balkans.
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.