U.N. Secretary-General Ban Ki-moon has used the official opening of the International Criminal Court's new headquarters to renew calls for more countries to join the world's first permanent criminal tribunal and cooperate in its investigations.

Ban called Tuesday's opening by Dutch King Willem-Alexander "a milestone in global efforts to promote and uphold human rights and the rule of law."

He says he will continue to urge U.N. member states that haven't joined the court to do so and called on countries "to extend their full cooperation" to the court, which has no police force of its own to make arrests and secure evidence.

The ICC's new home, which has been in use since January, is made up of six interconnected blocks built into North Sea dunes.