Governments agreed Tuesday to step up efforts to protect threatened tree species from illegal loggers amid warnings that criminal gangs are plundering the world's forests.

The 178-member Convention on International Trade in Endangered Species (CITES) agreed at a major wildlife conference in Bangkok to restrict cross-border trade in ebony from Madagascar as well as rosewoods from the same island, Southeast Asia and Central America.

"Never before have so many positive proposals to list tree species been adopted by CITES nations," said Juan Carlos Cantu of Defenders of Wildlife.

"Without the protection of CITES to regulate international trade, the unsustainable illegal harvest will bring these species to the brink of extinction in 10-20 years," he warned.

The proposals, adopted by consensus at the meeting in Bangkok, aim to help countries better regulate and monitor trade in the tropical hardwoods, making it harder for illegal loggers to sell their timber overseas.

They require countries to issue export permits to ensure the sustainability of the species in the wild, or face sanctions by members of CITES, a global treaty which protects some 35,000 species.

Experts said the listing of slow-growing timber species from Madagascar was particularly welcome as many have been hit hard by a rampant illegal international trade despite a domestic ban on exports of precious wood.

Madagascar faces "a crisis of illegal logging" owing to political instability and growing global demand for its wood, said Mark Roberts of the Environmental Investigation Agency, a wildlife campaign group.

"Wherever rosewood and ebony grow, forestry officials are grappling with the effects of illegal harvesting and trade, valuable resources plundered, involvement of organised crime and habitat loss," he added.

Experts say China has emerged as a major destination for timber from Madagascar and elsewhere, replacing traditional markets like Europe which has shifted towards sustainably managed wood.

"China has a very well developed processing industry," using timber for everything from musical instruments to furniture, said David Newton, an expert with wildlife trade monitoring group Traffic.

The UN Environment Programme estimates that between 50 and 90 percent of logging in key tropical countries of the Amazon basin, Central Africa and Southeast Asia is done by organised crime rings.

"Illegal logging is worth well over $30 billion annually to the criminals, whereas many of the poor people enlisted into these illegal activities get a pittance in return," said UNEP executive director Achim Steiner.