Organised crime is now a big player in illegal logging, which accounts for up to 30 percent of all wood traded globally, the UN and Interpol warned on Thursday.

In the mid-2000s, some tropical countries reported a fall in illicit forest clearance, but this may well have been a mirage, they said.

In fact, criminals laundered profits into tree plantation companies.

They used these as fronts for driving corridors into old forests, plundering trees which they frequently passed off as wood from sustainable sources.

"In many cases a tripling in the volumes of timber 'originating' from plantations in the five years following the law enforcement crackdown on illegal logging has come partly from cover operations to criminals to legalise and launder illegal logging operations," said the report, Green Carbon: Black Trade.

Between 50 to 90 per cent of logging in the Amazon basin, Central Africa and Southeast Asia is illegal, although not all of this is from organised crime, it said.

Globally, illegal logging is worth between $30 and 100 billion (25 and 77.5 billion euros) annually, or between 10 and 30 percent of all timber transactions.

Among examples cited in the report, some 3,000 companies in Brazil are under investigation for "eco-certifying" illegal timber and exporting it abroad.

"In Indonesia, the amount of logs allegedly produced through plantations increased from 3.7 million cubic metres (129 million cubic feet) in 2000 to over 22 million (770 million cu. ft.) in 2008," it said.

Less than half of these plantations actually existed, investigators believe.

Among the casualties are indigenous forest dwellers, who face rising violence from loggers, as well as biodiversity and the fight against global warming.

Deforestation accounts for an estimated 17 percent of all man-made carbon emissions and 50 percent more than those from ships, aviation and land transport combined, the report noted.

The report called for a greater policing effort against illegal logging syndicates, tax fraud, corruption and laundering.

It also suggested an independent rating of companies to discourage investors from funding illegal practices.

The report pointed to some encouraging initiatives, including the International Consortium on Combating Wildlife Crime (ICCWC), whose partners include among others Interpol and CITES, the Convention on International Trade in Endangered Species.

Another weapon is so-called REDD-plus, in which wealthy countries provide funds to poorer countries to encourage them to be custodians of the forests.

However, "if REDD-plus is to succeed, payments to communities for their conservation efforts need to be higher than the returns from activities that lead to environmental degradation," warned the report.

The report, authored by the UN Environment Programme (UNEP) and Interpol, was launched at the World Forest Conference at the Food and Agricultural Organisation (FAO) in Rome.