The riots in Hoorn on Friday evening which led to 12 arrests were mainly the work of a group of outsiders who had come to the town to cause trouble, Jan Nieuwenburg, the town’s mayor, said on Saturday.

Demonstrations for and against a controversial statue on the town’s main square passed off peacefully at separate locations outside the town centre in the late afternoon and early evening.

However the situation escalated when a group of 100 to 200 people, including local youngsters, marched into town shouting ‘away with JP Coen’. Police then intervened to stop the group, who began throwing rocks and cafe furniture, eyewitnesses said.

The mayor was forced to invoke his emergency powers to restore order.

Hoorn is the birthplace of Jan Pietersz Coen, a seafarer and governor of Indonesia when it was under Dutch rule.  He also led punishment expeditions against people on the Banda Islands, in which thousands died.

A statue to Coen was erected in the 19th century, even though his legacy was controversial in some quarters at the time. In 2011 there was a debate within the town council about having it removed. In the event, officials placed a sign on the plinth outlining Coen’s deeds.

If people want to have the statue taken away they should do so using democratic methods, such as a vote, Nieuwenburg said: ‘The riots are not a reason to have it removed.’