BEIJING, Sept 27 (Reuters) - A British frigate was sailing through the sensitive Taiwan strait on Monday en route to Vietnam, according to an official tweet from the vessel, amid heightened tensions between Taiwan and China. China claims Taiwan as its own territory and has stepped up military and political pressure to force the democratically ruled island to accept Chinese sovereignty. HMS Richmond had been deployed in the East China Sea taking part in United Nation"s sanctions enforcement operations against North Korea. read more