Some 500 left-wing protesters were detained and then freed on Saturday as the convention of the populist Alternative for Germany (AfD) party got underway in the southern city of Stuttgart.

"We will continue to keep an eye on some of them," said a local police spokesman, following scuffles between protesters and police as some 1,500 demonstrators attempted to interrupt the AfD gathering.

The AfD has courted controversy since its founding in 2013 as a euroskeptic answer to the political vacuum that arose to the right of the spectrum as Chancellor Angela Merkel's Christian Democrats (CDU) moved more to the left. Since ousting founder Bernd Lucke last summer, the right-wing party has managed to alienate itself further from the political mainstream by questioning the country's welcoming policy towards refugees and Islam, scoring large victories in several regional elections in the process.

Despite Saturday's violence, the AfD was determined to use the weekend's convention to script a new party manifesto, and some 2,000 party members were on hand to help decide the party's next direction. By Saturday evening, the populists had already agreed to maintain their opposition to the euro currency and condemn the European Union as a political entity.

Merkel: 'The do-nothing chancellor'

"We always wondered when the brave child will finally appear to voice the thoughts of the silent majority and declare that the 'chancellor of no alternatives'" doesn't know what she's doing, said party leader Frauke Petry as she opened the convention, referring to Merkel.

"And I think, this brave child is us," Petry added.

The party's position on Islam in Germany will be debated on Sunday, but Beatrix von Storch, a member of the European Parliament in Brussels for the AfD, has already dismissed the world's second largest religion as "not compatible with the German constitution."