The United Nations said on Monday that the number of people in Arab countries infected with HIV more than doubled to 470,000 in the eight years to 2009.
"The number of adults and children living with HIV has more than doubled between 2001 and 2009 from 180,000 to 470,000," according to data from UNAIDS, the UN programme on HIV and AIDS.
New HIV infections increased from 43,000 in 2001 to 59,000 in 2009, it said at a meeting in Riyadh on combatting AIDS, organised by the Arab League and the Saudi government.
The number of deaths from AIDS also surged from about 8,000 in 2001 to 24,000 in 2009.
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In Djibouti and Somalia, the percentage of infected people represents 2.5 percent and 0.7 percent of the countries' respective populations.
"These figures are very worrying and need an immediate response," it said in an Arabic-language statement.
The figures appear in contrast with the global trend.
UNAIDS said last week that 25 low- and middle-income countries had managed to at least halve their rate of new HIV infections since 2001, representing a reduction of 700,000 new HIV infections.
Globally, new HIV infections fell to 2.5 million last year from 2.6 million in 2010 and represented a 20-percent drop from 2001, it said.