Travellers from outside the EU are being turned away from airports and borders, after the 27-country bloc imposed a 30-day ban to halt the spread of coronavirus.
A group flying in from Turkey was turned away from Germanys biggest airport in Frankfurt late on Tuesday, DPA news agency reports.
EU leaders agreed that internal borders that have been erected in recent days should come down.
Many Europeans work across borders.
More than 185,000 people have been infected worldwide, according to the World Health Organization. Europe has been identified by the WHO as now the “epicentre of the epidemic”. Latest figures say some 3,400 people have died in Europe alone.
Belgium is the latest EU country to introduce a lockdown for its 11.4 million citizens.
People have been urged to stay at home as much as possible and only essential travel will be allowed. Most shops will close, but physical activity is allowed as long as people respect social distancing.
What has the EU agreed?
The 30-day entry ban will not affect Europeans going home or cross-border workers. UK citizens are also not affected by it because an interim Brexit deal still ties the UK to EU rules.
The ban specifically covers all EU states as well as countries within the Schengen border-free zone, including Iceland, Switzerland, Norway and Liechtenstein.
All citizens will be given help returning home, and Germany on Wednesday said it would continue a drive to fly home tens of thousands of tourists stranded abroad, from Morocco and Egypt to the Philippines and Argentina.
The Robert Koch Institute (RKI), the scientific body advising the government on health issues, has warned that Germany could see up to 10 million cases of coronavirus infections within the next two to three months unless the current containment measures are strictly followed.
Why are internal borders a problem?
Individual European governments have begun erecting patrols to stop citizens from other countries from entering.
Patrols appeared on Tuesday on the Spanish border with France, and Poland has seen traffic jams of up to 50km (31 miles) at some of its crossings as part of its health measures.
“It is absolutely crucial that we unblock the situation, because we know that too many people are stranded within the European Union and have a problem to go back home,” said European Commission President Ursula von der Leyen.
Long queues on Polish border
By Adam Easton, BBC News Warsaw
Some people are having to wait for more than 24 hours following the introduction of checks at midnight on Saturday.
Foreigners are temporarily banned from entering the country and returning Polish citizens must be quarantined for 14 days. Border guards wearing protective suits and face masks are taking the temperature of everyone crossing the border.
Thousands of foreigners are leaving Poland to return home and thousands of Poles are trying to get back in.
And then there are the trucks. The borders are still open to goods, but the authorities did not create special lanes for truck drivers to cross, so everyone is stuck in one line.
At the crossing in Jedrzychowice on the German border on Wednesday morning, people have been stuck in their vehicles overnight, many with nothing to eat or drink and with no access to toilets.
How bad is the situation in Europe?
In France, the number of confirmed cases in France grew by more than 16% on Tuesday, reaching 7,730, The death toll rose to 175, with 7% of the dead aged under 65.
In the UK, the number of dead has reached 71.
The number of confirmed cases in Spain has soared to more than 13,700.
Italy, which has registered the most cases outside China at more than 31,500, announced another surge in deaths on Tuesday, from 2,150 to 2,503.
Belgium announced four more deaths on Wednesday bringing the overall number to 14, with 2Read More – Source
