Vietnam customs officials on Monday said they had seized more than a tonne of ivory, believed to be from elephant tusks, being smuggled on the country\'s border with China. Around 221 tusk portions were discovered hidden on an iron boat that was intercepted by Vietnamese authorities as it tried to cross a river on the northern frontier with China late Saturday, an official from the local Quang Ninh customs department told AFP. Three people, including two Chinese nationals, were arrested and are currently in police custody, said the official, who declined to be named. \"We are investigating whether all of the tusks are from elephants as well as where they came from and were headed,\" he added. Ivory seizures are reported periodically in Vietnam, where customs officials last year seized two tonnes of elephant tusks illegally imported from Kenya and destined for China, according to state-controlled media. The global ivory trade has been banned since 1989 but there has been a dramatic surge in illegal trafficking since 2005. China is one of the world\'s biggest markets for ivory, which is used for home furnishings and jewellery. It is also popular in Vietnam.