The national war memorial on the Dam in central Amsterdam was sprayed with red paint in the early hours of Monday morning, just hours before the Remembrance Day commemorations.

The monument, where the king and queen and other dignitaries will lay wreaths on Monday evening, takes centre stage in the annual televised event, in which the Dutch remember their war dead with two-minutes silence.

Cleaners were out in force on Monday morning to remove the paint, which included the word “genocide”.

Amsterdam mayor Femke Halsema condemned the action as an “unbelievably cowardly act” in a message on social media. Prime minister Rob Jetten described it as “idiotic and completely unacceptable”.

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This is especially the case on May 4, Jetten said on social media. “Today, let us be united and reflect together in silence,” he said.

There have been continued efforts by some campaigners to widen the scope of the May 4 commemorations to remember all victims of war.

Last year the monument was attacked with red paint during a large pro-Palestine demonstration in the capital.

Police said later on Monday morning they were looking for three suspects caught on camera defacing the monument.