Iran has warned Britain that it should be “scared” of retaliation after Royal Marines seized an oil supertanker in Gibraltar.  “I am openly saying that Britain should be scared of Iran’s retaliatory measures over the illegal seizure of the Iranian oil tanker,” said cleric Mohammad Ali Mousavi Jazayeri.  The comments came after the UK-flagged Pacific Voyager tanker was mysteriously halted in the Persian Gulf early on Saturday - but was later confirmed to be "safe and well".  The ship was stopped as part of a routine procedure to adjust its arrival time at its next port of call, a UK Marine Trade Operations official said.  The UKMTO, which coordinates shipping in the Gulf, had been in direct contact with the vessel, the official said.  Iran earlier dismissed "fabricated" reports that the ship had been seized by its Revolutionary Guard forces.  “We have shown that we will never remain silent against bullying ...As we gave a staunch response to the American drone, the appropriate response to this illegal capture (of the tanker) will be given by Iran as well,” he said.  British Royal Marines seized the supertanker Grace 1 on Thursday for trying to take oil to Syria in violation of EU sanctions in a move which drew Tehran’s fury and could escalate its confrontation with the West.  A Gibraltar spokesman said the 28-member crew, who have remained on board the supertanker, were mainly Indians with some Pakistanis and Ukrainians.  Police and customs officials remained on board the vessel to carry out their investigation, but the Royal Marines were no longer present.  Iran downed a U.S. military drone on June 20 that it said was flying over one of its southern provinces on the Gulf.  Washington said the drone was shot down over international waters.  An Iranian Revolutionary Guards commander threatened on Friday to seize a British ship in retaliation for the capture of an Iranian supertanker by Royal Marines.