BRUSSELS (AFP) — Six people were wounded, two of them critically, in a knife attack at a Kurdish demonstration in the city of Antwerp Thursday, Belgian police said.

Officers arrested four people following the early evening attack near Antwerp’s Opera House and all the victims were taken to hospital, police spokesperson Wouter Bruyns told Agence France-Presse.

The motive for the attack was yet to be determined, he said, adding that police were combing through CCTV footage to ensure no other suspects had evaded arrest.

The stabbings took place at around 7:20 p.m. as the local Kurdish community demonstrated in support of Kurds in northern Syria, where Kurdish-led forces have been fighting a government advance.

According to initial findings, the suspects had mingled with the demonstrators before attacking them, authorities said.

Orhan Kilic, a spokesperson for Navbel, a group representing the Kurdish diaspora in Belgium, said families, women, young people, and children were attending the event.

“Just as the protest was disbanding, the Kurdish demonstrators were attacked by a group of men,” he added.

“These men had sneaked into the demonstration and suddenly pulled out knives and began stabbing people indiscriminately,” said Kilic.

“It is clear that this attack is not an isolated instance of senseless violence, but a motivated attack on a community.”

Police said the incident was being investigated as a case of attempted murder, “not terrorism.”

More than 134,000 people have been displaced in northeast Syria, according to the United Nations, after clashes and a fragile ceasefire deal between government troops and the Kurdish-led Syrian Democratic Forces (SDF).

Under military and political pressure from Damascus, which is seeking to extend its control across the country, the SDF has relinquished swathes of territory in recent days, withdrawing to parts of Hasakeh province, the Kurds’ stronghold in the northeast.