A confident far-right Alternative for Germany gathered Saturday to found its new youth organization as thousands of protesters converged on the western city of Giessen, some of them clashing with police.

A convention of the anti-immigration party, known by its German acronym AfD, started more than two hours late after groups of protesters blocked or tried to block roads in and around the city of some 93,000, delaying many delegates' arrival.

Footage showed protesters scuffling with two different couples who, according to local media DPA, were on their way to the convention.

Police said they used pepper spray after stones were thrown at officers at one location.

In another case, police said they used water cannons to clear a blockade by some 2,000 protesters after they ignored calls to leave.

Many people demonstrated peacefully. The regional government's interior minister, Roman Poseck, condemned the violence and put the total number of demonstrators at between 25,000 and 30,000.

AfD's leaders condemned the protests as the meeting opened at the city's convention center.

The new youth organization's predecessor, the Young Alternative — a largely autonomous group with relatively loose links to the party — was dissolved at the end of March after AfD decided to formally cut ties with it.