All 13 people arrested during the riots that broke out at an Eritrean festival at the weekend have been detained in custody, police said on Monday.

The suspects are all men, aged between 19 and 36. They are suspected of violent disorder and possessing weapons during the violence outside the Opera venue in The Hague on Saturday.

Eight officers were injured during the violence as police used tear gas to break up confrontations between supporters and opponents of the Eritrean government, one of the most oppressive regimes in the world.

Police and firefighters were pelted with stones, fireworks and bicycles, while several police vehicles and a bus were torched as the rioting spread along Fruitweg. Mayor Jan van Zanen ordered police to use tear gas to drive the rival groups apart.

MPs have called for a full investigation by the justice ministry into the weekend violence, including the question of whether the event should have gone ahead, following previous clashes at Eritrean festivals in Rijswijk, Amstelveen and Zaanstad.

‘Appalling’ violence

Van Zanen said the violence was “appalling and unacceptable”, adding it appeared to have been instigated by an anti-government youth organisation known as Brigade Nhamedu.

“The police and the council were aware of the gathering and took the necessary measures in consultation with the venue and the organiser of the gathering,” the mayor said.

“Based on this security was stepped up and police placed extra units on standby. After we received various reports in the early evening that youths from the Eritrean organisation Brigade Nhamedu were seeking a confrontation, an emergency order was issued.”

Kebrom Girmayy, of Eritrean Human Rights Defenders in the Netherlands, told Nieuwsuur he was “shocked” by the events, but called on the Dutch authorities to investigate the reasons behind the tension in the community.

“We shouldn’t be bringing what is happening in Eritrea over here. It’s a different society and we should respect it,” he said.

“I apologise to the Dutch people. They are kind people. But they need to do more investigating into what the problem is with these young people. This didn’t start yesterday.”

Mirjam van Reisen, professor of international relations at Tilburg University, said the violence could have been stoked by the Eritrean regime and a broader investigation was needed.

“We have seen in previous incidents that the regime trained and deployed paramilitary groups to start the riots,” she said.