LONDON (Reuters) – A Spanish warship tried to order commercial shipping to leave anchorages in British waters near Gibraltar but was challenged by the British navy and sailed away, Gibraltar said, the latest example of tension over the strategic port as Brexit approaches.

The Spanish ship tried to order ships to leave their anchorages on the eastern side of the Rock, but the ships stayed in position, Gibraltar’s authorities said. After being challenged by the British navy, the Spanish warship then sailed slowly along the coast with its weapons uncovered and manned.

Spanish authorities did not immediately comment on the issue.

Tensions over territorial waters around the peninsula in southern Spain often erupt between Spanish and British vessels. Gibraltar, overlooking the strait between the Atlantic Ocean and Mediterranean Sea, has been ruled by Britain since 1713.

Its status and the status of its 30,000 residents have been gaining attention as Britain’s exit from the European Union approaches on March 29, raising questions about free movement across its land and sea borders with Spain.

“There is only nuisance value to these foolish games being played by those who don’t accept unimpeachable British sovereignty over the waters around Gibraltar,” a spokesman for Gibraltar said.

Spain has already secured a right of veto over whether future Brexit arrangements can apply to Gibraltar. Prime Minister Pedro Sanchez held up an agreement on Britain’s withdrawal treaty in November over the issue and said Spain would seek joint sovereignty after Britain leaves the EU.

(Reporting by Guy Faulconbridge; additional information by Jose Elias Rodriguez; Editing by Kate Holton and Peter Graff)