The UK government has said it is “deeply concerned” about Iran’s “unacceptable” seizure of a British-flagged tanker in the Strait of Hormuz, BBC News reported.

Foreign Secretary Jeremy Hunt has warned of “serious consequences” if the situation is not resolved quickly.

Iran said the ship was “violating international maritime rules.”

The tanker Stena Impero was seized Friday by the Iranian Revolutionary Guard, according to Fars news agency.