The Antwerp diamond district heightened security after a Muslim group said terrorist attacks there are “almost unpreventable.”

Ahmed Azzuz, the leader of the Arab European League, a militant group, told a European publication that “the Jewish community in Antwerp [should] cease its support of, and distance itself from, the state of Israel. If not, attacks in Antwerp are almost unpreventable.”

The Antwerp Diamond High Council (HRD) said it had referred the incident to the Belgian public prosecutor. “Security is something everyone is concerned about these days, and we thought it was important that we respond in a forceful and direct way,” says HRD spokesman Youri Steverlynck.

The city has assigned more police to the diamond district, and Belgian Prime Minister Guy Verhofstadt later reiterated his government’s commitment to the industry’s security. “The fact that there was such a strong reaction—with more police on the street—has comforted people,” Steverlynck says. “There is no panic, and everything is under control.”

A 1981 terrorist bombing in the Antwerp diamond district killed three people.