A Spanish humanitarian group dedicated to saving migrants at sea says one of its boats has been denied permission to set sail from the port of Barcelona.

The Associated Press has seen the order sent by Spanish authorities to the aid group Proactiva Open Arms saying that its boat violated maritime regulations on past rescue missions.

The order says that on its last mission the boat violated "the obligation to leave those rescued at sea at the nearest port" when in December it brought some 300 migrants it had saved near Libya back to Spain.

The aid group has appealed the decision, arguing Monday that it only came to Spain after both Malta and Italy had turned it away.

Spain has allowed rescue boats rejected by other countries to dock in recent months.