Beijing has imposed a one-year ban on imports of ivory carvings as critics say rising Chinese demand threatens African elephants with extinction, but campaigners described the move as "more symbolic than effective" Friday.

The measure came days ahead of a visit to China by Britain's Prince William, who has campaigned against illegal wildlife trafficking and is expected to speak on the issue during a stop in the southwestern province of Yunnan next Wednesday.

The ban took effect Thursday and was announced by China's State Forestry Administration in a statement on its website.

China is a signatory to the Convention on International Trade in Endangered Species (Cites), but conservationists say it is the world's largest consumer of illegal ivory, with skyrocketing demand leading to the slaughter of tens of thousands of African elephants each year.

Sammi Li, a spokeswoman for TRAFFIC, the wildlife trade monitoring network, welcomed the import ban as sending a message and "recognition by China of their role in the illegal ivory trade".

But she told AFP: "The actual volume to be banned is rather small, so the ban is more symbolic than effective."

"It is hugely optimistic sign but much more action is still needed," said Ian Douglas-Hamilton, who founded Kenya-based Save the Elephants.

The ban was a "significant step in the right direction, signalling a growing realisation in China of the role they play in the demand for ivory," the zoologist said, calling for a total ivory ban.

"One year is not enough," said Paula Kahumbu, who heads the Nairobi-based conservation organisation WildlifeDirect.

"China has been denying for a long time that the demand for ivory has been the cause of the killing of elephants," Kahumbu told AFP.

"It's a very strong signal to the consumers of ivory that a complete ban is coming. I believe that they will soon ban the importation of ivory completely, and even the domestic trade."

- 'Out of control' -

Most illegal ivory is smuggled raw, and China has a significant domestic processing industry.

The country has a long tradition of ivory carving and regulated sales are legal, while Chinese collectors see the items as a valuable investment.

The raw material is often intricately carved to depict anything from devotional Buddhist scenes to wildlife and bizarre fantasies, as well as more mundane household objects such as chopsticks.

Under Cites, almost all international commerce in ivory is banned, although some limited categories such as licensed hunting trophies are legal and there have been occasional approved "one-off" sales of stockpiles by African countries.

Campaigners condemn such disposals as actually providing cover to the illegal trade.

The one-year timeframe for the ban on carving imports "is designed to assess the effects", Xinhua reported, but what impact it would have -- if any -- was unclear.

An official at the State Forestry Administration told AFP that China's last major legal ivory acquisition was in 2008, when 62 tonnes were purchased at a one-off auction, and since then "there have not been significant imports".

China has come under increasing international pressure on the issue in recent months.

Last year, Prince William appeared in an advert against the illegal wildlife trade along with footballer David Beckham and Chinese basketball superstar Yao Ming.

A joint report in December from Save the Elephants and The Aspinall Foundation campaign groups found that more than 100,000 wild elephants were killed from 2010 to 2012, with the slaughter largely fuelled by the "out of control" illegal ivory trade in China.

China is making efforts to stem the trade, the report's authors said, but the measures were not going far enough.

Researchers said prices for raw ivory in China had risen from $750 (550 euros) per kilo in 2010 to $2,100 (1,540 euros) in 2014.

"Every metric on the ivory trade has exploded upwards in recent years," they said.

But Chinese officials have denied that demand in the country is rising.

Meng Xianlin, executive director-general of the Endangered Species Import and Export Management Office of China, told the state-run China Daily newspaper that "the scale of illegal ivory production is way smaller than legal production".

Wildlife smuggling cases in China fell 70 percent last year from 2013, the paper reported.

Chinese foreign ministry spokesman Hong Lei said Thursday that bringing an end to poaching and the illegal ivory trade "requires joint efforts from all parties".

"China advocates that the international community make joint efforts to protect the endangered species of elephants," he said.