As Reuters reported, North Korea's foreign ministry rejected UN Security Council resolutions against it, which the US cited when seizing the ship, as violating its sovereignty.
Namely, according to the US, a North Korean cargo ship was seized and impounded to American Samoa. The US accused the ship of illicit coal shipments, thus violating sanctions and was first detained by Indonesia in April 2018.
A year earlier, Kim Jong Un and Donald Trump had met in Singapore to set out new relations and a peace regime on the Korean peninsula. However, tensions have increased once again, while the US announcement of the ship seizure came a few hours after the North Korea fired two short-range missiles.
In addition, a North Korean foreign ministry official opposed to the US's statement, which said that North Korea subjected its people to violations of human rights, including 100,000 in political prison camps.