Britain has expressed deep concern over Iran's unacceptable seizure of its flagged tanker in the Gulf.

British spokeswoman told BBC that the action is a clear challenge to international freedom of navigation.

European Union has expressed its deep concern over the seizure of a British-flagged tanker by Iran in the Strait of Hormuz.

In a statement in Brussels today, the EU's Foreign Affairs office said in an already tense situation, this development brings risks of further escalation and undermines ongoing work to find a way to resolve current tensions.

Meanwhile, Iran said the ship was violating international maritime rules.