Ivory tusks seized during an anti-smuggling operation are displayed during a Hong Kong Customs press conference on October 20, 2012 Officials travelling to Tanzania with Chinese President Xi Jinping went on a buying spree for illegal ivory, an environmental activist group has said. The delegation bought so much ivory prices in the local market soared, the Environmental Investigation Agency (EIA) said in a report. Tanzania rejected the report as "stupid nonsense". China said the allegations were "groundless". Conservationists say demand for ivory in China is fuelling poaching. In recent years, poaching has increased across sub-Saharan Africa, with criminal gangs slaughtering elephants for ivory. Tanzania is the largest source of poached ivory in the world, according to the EIA. 'Security checks averted' The EIA report cited a trader in Tanzania's main port city, Dar es Salaam, named as Suleiman Mochiwa, who met undercover investigators. He said that when the Chinese government and business delegation arrived, ivory prices in the local market doubled to $700 (£438) per kilo during the visit. Earlier this year China destroyed a large quantity of confiscated ivory for the first time "The [delegation]... used the opportunity to procure such a large amount of ivory that local prices increased," the report says. Investigators alleged that the Chinese buyers could take advantage of a lack of security checks for those in the country on a diplomatic visit.