As many as 10,000 people demonstrated in Vienna against a visit by Turkey's strongman Prime Minister Recep Tayyip Erdogan, organisers and police said.
Erdogan has been accused of autocratic tendencies in his home country and a similar trip to Germany last month ruffled feathers after he spoke out against assimilation of Turkish immigrants.
Yesterday, he addressed a crowd of some 6,000-7,000 supporters from Austria's 250,000-strong Turkish minority in a sports arena, police said.
Erdogan is touring European countries with large Turkish populations ahead of a widely expected run for the presidency in August.
A further 10,000 people watched his speech on a big screen outside the venue.
Police said they used pepper spray after a "minor incident" when a bottle was thrown at the protesters in the Austrian capital, most of whom were from the local Turkish community. No injuries were reported.
Austria's government had warned Erdogan against making provocative comments, and he appeared to heed the advice telling the crowd, "no one has anything to fear from us".
But the visit nonetheless drew sharp words from Austrian Foreign Minister Sebastian Kurz, who said the meeting "clearly shows that the Turkish prime minister has brought the election campaign to Austria and has also, as a result, caused disorder.
"We refuse to accept that, and the only thing I can say is that respect for a country does not look like this," he told journalists.
Trumpeting Turkey's economic growth under his stewardship, Erdogan said that Europe needed his country.
"Europe does not end where the river Danube flows into the Black Sea but begins where the Euphrates and Tigris begin," he said.
