THE HAGUE, Netherlands (AP) — A bomb that was pushed through a letter slot exploded at the party headquarters of Dutch Prime Minister Rob Jetten but didn’t injure anyone, and the centrist leader vowed Friday not to be intimidated by the attack.

Police said they had arrested a 37-year-old suspect in the bombing late Thursday at the headquarters of the centrist D66 party in The Hague, but declined to release any further details including any suspected motive.

The attack took place during a meeting of about 30 members of the party’s youth wing, who were startled but unharmed, Jetten said.

Jetten, who took office in February, told reporters during his weekly news conference that it was “pretty futile if you think you can intimidate politicians with these kinds of actions.”

The leaders of other political parties joined Jetten in condemning the attacks.

Center-right VVD leader Dilan Yeşilgöz called the attack a “cowardly act” on social media. Opposition leader Jesse Klave from the left party PRO called the bombing “a direct attack on our democracy and the rule of law.”

It was the second time the building in the city center of The Hague had been attacked in less than a year. In September a right-wing demonstration erupted into violence during which rioters vandalized the office, just weeks ahead of the general election.

Jetten, who became the Netherlands’ youngest-ever prime minister in February, was equally defiant in the autumn, calling the attackers “scum” in a post on social media.