DÜSSELDORF, Germany  — A Syrian man suspected of belonging to the Islamic State group pleaded guilty to the murder of three people at a German festival as his trial opened on Tuesday.

Issa Al Hasan faces charges including three counts of murder, 10 counts of attempted murder and membership of a foreign terror organization. In a statement read out by his lawyer, Hasan admitted he had “committed a grave crime” and that “three people died at my hands.”

The stabbing in August in the western city of Solingen was one of a string of attacks that shocked Germany and stoked security fears.

The suspect, who was 26 at the time of the attack, was an asylum seeker from Syria who had been slated for deportation.

German authorities’ failure to remove him from the country fired a bitter debate over immigration in the run-up to national elections.

Hasan is alleged to have set out to harm “nonbelievers” at the summer “festival for diversity” in the center of the western city of Solingen.

The accused “saw them as representatives of Western society” and sought “to take revenge against them for the military actions of Western states,” prosecutors have said.

A member of ISIS whom Hasan had contacted the same month as the attack allegedly encouraged him to go ahead with the plan and promised him that the group would claim it and use it for propaganda purposes.

The group later said in a statement via its Amaq news agency on the Telegram messaging app that an ISIS “soldier” had carried out the attack in “revenge” for Muslims “in Palestine and everywhere.”

Prosecutors say Hasan filmed videos in which he pledged allegiance to ISIS and forwarded them on to his ISIS contact just before he committed the attack.