Greenpeace activists on speedboats asked the tanker not to unload its cargo over the radio, while a handful of others held a small protest at the port entrance.
"This cargo is full of Russian gas from Yamal (Russia). Gas and oil are financing the Russian regime's war in Ukraine," they said. "We stand with the people of Ukraine and people of Russia who have not chosen the war. We ask you not to unload your cargo."
The Guardian newspaper reported the vessel had been on its way to the Isle of Grain, in southeast England, with a consignment of liquefied natural gas for Centrica, the owner of British Gas.