Chinese officials and businesspeople used a state trip by President Xi Jinping and other high-level visits to smuggle ivory out of Tanzania, an environmental watchdog has said.

The accusation casts doubt over China's efforts to end the illegal trade that has led to rampant elephant poaching throughout Africa.

China is the world's largest importer of smuggled tusks, and Tanzania is the largest source of poached ivory, the London-based Environmental Investigation Agency (EIA) said on Thursday.

Poaching in Tanzania alone has killed half of the country's elephants in the past five years, the group said in the report.

It said Chinese-led criminal gangs conspired with corrupt Tanzanian officials to traffic huge amounts of ivory, some of which was loaded in diplomatic bags on Xi's plane during a presidential visit in March 2013.

China's Ministry of Foreign Affairs denied the report. Hong Lei, a spokesman, said China has "consistently" opposed poaching and has sought to crack down on ivory smuggling.

"The report is groundless, and we express our strong dissatisfaction," he said.

China cracks downs on poached ivory

Meng Xianlin, director-general of the Endangered Species Import and Export Management Office of China, said he has never heard of involvement of Chinese delegations in ivory trade.

"I don't think there's hard evidence, and I have not seen such cases," Meng said.

"Allegations without evidence are not believable, and I don't think it is appropriate for (EIA) to come up with this mess."

He said that the EIA has been "unfriendly to China for quite some time," calling the allegations irresponsible.

Carved ivory has historically been highly prized in China, and its scarcity has turned it into an investment choice akin to gold and silver.

In its report, EIA said its investigators learned as early as 2006 that some staff members of the Chinese embassy in Tanzania were major buyers of illegal ivory.

Increase in prosecutions

It said Chinese government officials and businesspeople in the entourage during Xi's 2013 state visit used the opportunity to buy such a large amount of ivory that local prices doubled.

Two traders claimed that Chinese buyers, two weeks before the visit, began purchasing thousands of kilograms of ivory, which was later sent to China in diplomatic bags on the presidential plane, the EIA report said.

"Your president was here," one of the traders told investigators in hidden video footage provided by the agency.

"When he was here, many kilos go out."

"When the guest come, the whole delegation, that's time ... the business go out," the trader said.

It said that in December 2013, one dealer boasted of having sold $50,000 worth of ivory to Chinese navy personnel on an official visit in Tanzania's port city of Dar es Salaam.

In China, authorities have campaigned against illegal ivory. Six tonnes of illegal ivory was pulverised earlier this year in the southern city of Dongguan, and Chinese courts have stepped up prosecutions of illegal ivory trade.

Criminal cases involving endangered animals and the illegal ivory trade rose 9.6 percent in the first months of last year, compared with the same period a year earlier.

The government also warns Chinese tourists in Tanzania not to purchase ivory products or face stiff penalties.

Source: Agencies