Japan will prolong economic sanctions against North Korea for two more years and take additional financial steps to punish it for violating a U.N. resolution against nuclear testing, officials said Friday.

In the meantime, all exports to and imports from North Korea remain banned and North Korean ships are still not allowed to call at Japanese ports.

The bans were to expire on April 13, but the Cabinet extended them to send a strong message to the reclusive state to stop its “provocative acts” and improve relations.

Among the new steps, Japan froze the assets of three North Korean-related groups and seven individuals to comply with a U.N. resolution against the nuclear test Pyongyang carried out in February. It also urged across the country to terminate any correspondence with North Korean banks.