The World Health Organization report, based on data collected between 2002 and 2006 on 90 000 TB patients in 81 countries, estimated there are nearly half a million new cases of MDR-TB a year, which is about 5 percent of the 9 million new TB cases of all types.

The report also found that extensively drug-resistant tuberculosis, or XDR-TB -- a virtually untreatable form of TB -- has been recorded in 45 countries.

For the first time, the TB survey included an analysis of XDR-TB, however, because few countries are currently equipped to diagnose it because of a lack of equipment and trained personnel.

The true scale of TB remains unknown in some places of the world. Only six countries in Africa -- with the highest incidence of TB in the world -- were able to provide drug resistance data.

"TB drug resistance needs a frontal assault. If countries and the international community fail to address it aggressively now we will lose this battle," Dr. Mario Raviglione, director of the WHO Stop TB department said in a statement.