BEIJING - The number of people estimated to be living with HIV in China has risen to 700,000, with increases among intravenous drug users and sex workers, according to a report released Thursday by the UN and the Chinese government.

Earlier Thursday, the official Xinhua News Agency mistakenly reported the number was as low as 223,501. That figure represents the government's tally of reported HIV cases. The joint UN report provides an estimate based on collected data.

In 2005, the government estimated 650,000 people to be living with HIV, the virus that causes AIDS.

The 50,000 new estimated cases in 2007 were mainly among intravenous drug users and sex workers, based on a joint assessment by UNAIDS and a committee of the State Council, China's Cabinet.

"China's HIV epidemic remains one of low prevalence overall, but with pockets of high infection among specific sub-populations," said the 38-page report, which is set to be officially released Saturday, to coincide with World AIDS Day.

"A number of core challenges remain," it said, including the need for better advocacy and education, improved treatment and care, and more focused education and discrimination reduction.

The report also said that the number of cases of HIV officially reported totaled 223,501.

HIV gained a foothold in China largely due to unsanitary blood plasma-buying schemes and tainted transfusions in hospitals. But China's Minister of Health Zhu Chen told reporters Thursday that these practices had been "effectively contained." He did not give any other details.

After years of denying that AIDS was a problem, Chinese leaders have shifted gears dramatically in recent years, confronting the disease more openly and promising anonymous testing, free treatment for the poor and a ban on discrimination against people with the virus.

The topic, however, still remains sensitive and authorities regularly crack down on activists and patients seeking more support and rights.

In 2004, China scaled back the estimated number of people infected with HIV, from nearly 1 million to 840,000, and then further lowered the figure to 650,000 in 2005.

Experts have said the figures are probably accurate and reflect a change in the way data are collected.

According to Thursday's report, there was an increase in the number of infections through heterosexual sex, as well as transmissions between sex workers and their clients.

"The issue of stigma and discrimination is really a complex challenge," Khalid Malik, the UN resident coordinator in China, said, adding that HIV/AIDS remained a "large challenge" in China.

Chen, the health minister, said the leadership was strengthening its commitment to HIV/AIDS at different levels of the government and among the high risk groups.

He said the amount spent in 2007 has risen to $126 million from $114 million in 2006.

Global health officials said earlier this month that the estimated number of people infected with HIV around the world fell from almost 40 million last year to about 33.2 million this year.

Previous estimates were largely inflated and the new numbers are the result of a different methodology, which show that the AIDS pandemic is losing momentum.

The old AIDS numbers were largely based on how many infected pregnant women were treated at prenatal clinics, as well as projecting the AIDS rates of certain high-risk groups like drug users to the entire population at risk. Officials said those figures were flawed, and are now incorporating more data like national household surveys.