Germany's anti-Islam PEGIDA movement has staged rallies in several cities across Europe to protest against the arrival of hundreds of thousands of migrants from the Middle East and Africa.
The movement, whose name stands for Patriotic Europeans Against the Islamisation of the West, originated in the eastern German city of Dresden in 2014, with supporters seizing on a surge in asylum seekers to warn that Germany risks being overrun by Muslims.
After almost fizzling out early last year, the movement has regained momentum amid deepening public unease over whether Germany can cope with the 1.1 million migrants who arrived in the country during 2015.
"We must succeed in guarding and controlling Europe's external borders as well as its internal borders once again," PEGIDA member Siegfried Daebritz on Saturday told a crowd on the banks of the River Elbe who chanted "Merkel must go!"
Police in Dresden declined to estimate the number of protesters. German media put the number at up to 8000, well below the 15,000 originally expected by police.
Protests also took place on Saturday in other cities, including Amsterdam, Prague and the English city of Birmingham.
In Calais, in northern France, more than a dozen people were arrested during a protest that was attended by more than a hundred people despite being banned, local authorities said.
Thousands of migrants fleeing war and poverty in Africa and the Middle East camp out in Calais, hoping for a chance to make the short trip across the English Channel to Britain.
In Prague, an estimated 2200 people including both supporters and opponents of Pegida held a series of rival demonstrations around the Czech capital.
Police had to intervene in one march when supporters of the migrants came under attack from around 20 people who threw bottles and stones.
In Warsaw, hundreds of people waved Polish flags and chanted "England and France are in tears, that's how tolerance ends".
"We're demonstrating against the Islamisation of Europe, we're demonstrating against immigration, against an invasion," Robert Winnicki, leader of Poland's far-right Ruch Narodowy (National Movement), told demonstrators.