Amsterdam’s mayor says he has ordered extra security measures at the city’s Jewish monuments on 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.

Amsterdam 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.

A police van was stationed outside the Jewish Historical Museum Friday morning.

Spokespeople for the city and the museums declined to comment on what additional measures are being taken, citing security concerns.

(AP)