Many delegates arrived at the conference venue before protesters set up blockades, allowing this weekend's two-day meeting to begin on time.
Police said around 31,000 people took part in largely peaceful demonstrations, while organisers put the figure at more than 50,000.
Protesters blocked roads into the city, with some abseiling from a motorway bridge, while others staged sit-in protests that disrupted bus and tram services.
"It's important to send a signal against the shift to the right," said 19-year-old demonstrator Lene Krug. "The AfD is an anti-democratic party that spreads hate."
State elections
The AfD, which has topped recent national opinion polls, is hoping to make further gains in state elections in eastern Germany later this year. Polls suggest it could win an outright majority in September's election in Saxony-Anhalt.
The party came second in last year's national election with 20 percent of the vote, behind Chancellor Friedrich Merz's conservative CDU/CSU alliance.
AfD co-leader Alice Weidel rejected accusations that the party was anti-democratic.
"We are the new people's party in Germany," she told delegates. AfD co-leaders Alice Weidel and Tino Chrupalla were both re-elected at the party's congress.
Migrant centre in Germany feels the heat from rising far right
Leadership confirmed
Weidel and co-leader Tino Chrupalla were re-elected for another two-year term during the congress.
"Perhaps we'll soon be able to govern on our own," Chrupalla said. "That would be the right signal to the democracy-despisers out there who wanted to stop our party conference."
Critics accuse the AfD of downplaying Nazi crimes and maintaining links with right-wing extremists – allegations the party rejects.
In 2018, Alexander Gauland, then co-leader of the AfD party, described the Nazi era as "a speck of bird poop" in Germany's otherwise grand 1,000-year history.
A proposal to relax rules governing members' links to extremist groups was withdrawn after pressure from the party leadership, although Weidel said the policy would be reviewed within a year.
(with newswires)


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