A meeting of Germany's right-wing anti-immigrant party Alternative fur Deutschland (AfD) has been marred by clashes outside the venue in Stuttgart.
About 1,000 police were deployed to keep supporters apart from left-wing protesters, who blocked roads, burned tyres and threw firecrackers.
About 400 protesters were temporarily detained as the conference began.
Delegates are due to vote on Sunday on a manifesto which some members want to endorse an openly anti-Islamic stance.
The party wants to ban the burka and outlaw minarets in Germany.
A police spokesman said protesters threw stones at officers and let off fireworks in their direction.
Riot police used tear gas, pepper spray and a water cannon to keep the protesters back.
One demonstrator, Dominik Schmeiser, said: "We are united by our conviction that we cannot let the AfD go unchallenged, and that it is a party which is not only racist, but which is engaged in the politics of exclusion and social division.
"We will not allow ourselves to be divided and we stand together for a compassionate society."
Despite the protest, the conference began as planned.
The party's leader Frauke Petry attacked the German chancellor Angela Merkel, saying the "silent majority" thought she was "nothing but naked".
She said the AfD wanted to make a big impact in German politics.
"In the future we do not want to remain sitting in parliament as a junior partner, a small opposition party," Ms Petry said.
The AfD achieved gains in all three states taking part in regional elections last month, claiming almost a quarter of the vote in the relatively poor eastern state of Saxony-Anhalt.
It had campaigned against what it called Mrs Merkel's "catastrophic" decision to accept a million migrants and refugees in 2015.
In Saturday's conference, the party must agree a manifesto ahead of next year's general election.
Proposals include withdrawal from the euro and the reintroduction of conscription, but there are splits within the party, including between its less hardline wing and the leadership.
Before the meeting, police encircled groups of demonstrators in a technique known as kettling. Some protesters were seen being dragged away, as others chanted "Shame on you" at officers.
March state election results
More on AfD
- Founded in 2013 by Bernd Lucke, Alexander Gauland and Konrad Adam to oppose German-backed bailouts for poorer southern European countries
- Mr Lucke, seen as a moderate, wanted Germany out of the euro but his colleagues were unhappy that he wanted to focus exclusively on euro-related issues
- He quit the party in early July 2015, arguing it was becoming increasingly xenophobic
- Right-winger Frauke Petry replaced him as party leader
- It became the first anti-euro party to win seats in a German regional parliament, receiving almost 10% of the vote in the eastern German state of Saxony in 2014, and went on to win seats in four other states' parliaments in 2014 and 2015
- The party had seven MEPs elected in the 2014 European elections (including Mr Lucke), but only two remain party members
- AfD was part of the European Conservatives and Reformists Group, like the UK's Conservatives, but one of its two MEPs has recently been expelled from the group over comments on shooting refugees