BERLIN (AP) — Two teenage Islamic extremists were allegedly behind an explosion in a Sikh temple in the German city of Essen that wounded three people, the city's police president said Thursday, calling the blast an "act of terror."

Essen police president Frank Richter told reporters the two 16-year-old boys from Essen and nearby Gelsenkirchen, whose identities weren't given in accordance with German privacy laws, were under arrest. One had come forward while the second was arrested at his parents' home, the German news agency dpa reported.

"We must assume that this is an act of terror," Richter said.

Police said both had clear links to Islamic extremism, and they were investigating if the two self-radicalized or were part of a bigger group.

"We assume there will be more arrests," Richter said, adding that 120 officers were investigating the bomb that exploded Saturday in the western city. Both boys had "partially admitted" the attack, but had not talked about their motives, he said.

The victims were among 200 people who had attended a wedding earlier at the temple. The cleric who had officiated, a 60-year-old man, suffered serious wounds and remains hospitalized. Two other men, aged 47 and 56, suffered slight injuries.

Police in Essen said they're still clueless as to why the Sikh community was targeted by the attackers. There are between 8,000 to 15,000 Sikhs in Germany, dpa reported.

The interior minister of the western state of North Rhine-Westphalia, Ralf Jaeger, said the two teenagers had attracted the attention of police before the attack. Dpa reported they had links to Salafist groups.

"I find it shocking that people who grew up among us are in a position and willing to build bombs and risk the lives of others," Jaeger said.

Residents of Essen are trying to organize a rally Saturday to express their solidarity with the Sikh community, dpa reported.