At least six police officers were injured and 13 suspects arrest after rival groups of Eritreans fought running battles in The Hague in the early hours of Sunday, torching police cars and hurling rocks.
Special police units fired tear gas at the rioters, who police said were pro- and anti-Eritrean government groups attending a meeting in The Hague.
"During the riots, stones, fireworks, and other items were thrown at police officers and the fire brigade. Several rioters had weapons to hit people with," police said.
The rioters set two police cars and a tour bus ablaze.
During the disturbances, two officers sustained injuries to their hands and another to her teeth. A fourth was hit by a police car in the chaos.
Police in a later statement said another agent became unwell because of the tear gas, while a sixth officer was wounded in the knee.
"Out of nowhere, our colleagues were confronted with very intense and serious violence," said police commander Marielle van Vulpen.
Police made 13 arrests and have called for witnesses and video footage, as they investigate the riots.
The suspects were men between 19 and 36 years old, a statement said.
"The violence used against police officers and equipment is appalling and unacceptable," said the city's mayor Jan van Zanen.
Anti-immigration far-right leader Geert Wilders posted social media images of the riots with a caption in capital letters: "Arrest and Deport".
He then wrote on X, formerly Twitter: "The Netherlands has really had it up to here with this."
"Why is half the world allowed to come here to tear down our country, fight amongst themselves, throw stones at the police and set their cars on fire?"
"I want to become the prime minister who finally brings some order to this," added Wilders, who won elections in November but is struggling to form a coalition government.
There are some 25,000 Eritreans living in the Netherlands, according to official government figures.
Pro- and anti-government groups have previously clashed, including last year when several people were stabbed ahead of an event to celebrate Eritrean independence from Ethiopia.