A 26-year-old man has given himself up and confessed to a mass knife attack at a street festival in Germany, police said on Sunday.

“The involvement of this person is currently under intensive investigation,” prosecutors and Düsseldorf police said in a joint statement.

Prosecutors have opened an investigation into “participating in a terrorist organisation”.

Three people were killed and another eight injured in the city of Solingen during a festival to celebrate its 650-year history, in what Chancellor Olaf Scholz described as a “horrific act”.

The Islamic State group on Saturday claimed responsibility for the bloodshed, but did not immediately provide any evidence of a relationship with the attacker.

Those killed were two men aged 56 and 67, and a 56-year-old woman, officials said. Four of the injured are still in a serious condition. All of the victims were stabbed in the neck, police have said.

“The man we’ve really been looking for the whole day has just been taken into custody,” Herbert Reul, the interior minister of North Rhine-Westphalia state, told ARD public TV late on Saturday.

Germany’s Bild and Spiegel news websites reported that the suspect surrendered himself in dirty blood-stained clothes.

Police described him as Syrian, and German media reported that he arrived in Germany in December 2022, after leaving the war-torn country.

Bild reported that special task force (SEK) officers stormed a refugee centre the suspect was associated with, detaining someone there.

Police also arrested a 15-year-old boy who is alleged to have known about the attack in advance.

The refugee centre is located about 300m (984ft) from Fronhof – Solingen’s central market square where people were stabbed on Friday night – according to Bild.

Solingen – a city famous for its steel industry – has about 160,000 inhabitants. It lies about 25km (15 miles) east of Düsseldorf.

The city’s authorities asked people to leave the Fronhof area after the attack at about 22:00 local time (21:00 BST) on Friday.

The planned three-day celebrations of the city anniversary – for which about 75,000 people had been expected – were cancelled after the attack.

Solingen Mayor Tim Kurzbach later said that “all of us in Solingen are in shock, horror and great sadness.

“It breaks my heart that an attack has happened in our city. I have tears in my eyes when I think of those we’ve lost.

“I pray for all those still fighting for their lives. Also my greatest sympathy for all those who had to experience this, these images must have been horrific.”

People have been bringing flowers and candles to the site of the attack that shocked the entire country.

Players from Germany’s top Bundesliga football league wore black armbands during Saturday’s matches.