Dutch police on Thursday arrested around 30 Greenpeace activists, including the captain of the lobby group's ship Rainbow Warrior, as they tried to stop a Russian tanker delivering Arctic oil from docking. "The captain has been arrested and the ship is being taken elsewhere else," police spokesman Roland Eckers told AFP of the Rainbow Warrior, adding that 30 others were arrested for trespassing or using inflatable boats to prevent the Russian tanker from docking at Rotterdam harbour.