AMSTERDAM (AP) — Amsterdam’s mayor says he has ordered extra security measures at the city’s Jewish schools, synagogues, and monuments — including the Anne Frank House — on the advice of the national anti-terrorism office.

In a letter to the city council, Eberhard van der Laan said he is not aware of any concrete threat to Jewish places of interest, but an attack is “conceivable” following an attack on the Jewish Museum in Brussels, Belgium, last month which left three people dead.

Buildings such as the Anne Frank House Museum and the Jewish Historical Museum already have considerable protective measures such as metal detectors and bullet-resistant glass.

Spokespeople for the museums and the city said they would not comment on security issues. But Van der Laan later told local television station AT5 he had ordered a permanent police presence outside major Jewish sites for the time being.

A police van was seen parked outside the Historical Museum Friday morning, and a temporary police booth was placed outside the Anne Frank House Friday afternoon.

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