The UN Human Rights Council agreed on Thursday to a U.S.-backed proposal to establish a UN human rights investigator for Iran, the first in a decade.

The 47-member Geneva forum approved the resolution by 22 votes in favor, 7 against and 14 abstentions, its president, Thai Ambassador Sihasak Phuangketkeow, announced.

The text voiced concern at Iran's crackdown on opposition figures and increased use of the death penalty and called on the Islamic Republic to cooperate with the UN envoy to be named to the independent post.

The United States announced its strong support the proposal that was drafted by Sweden earlier this month.

U.S. ambassador Eileen Donahoe told a news briefing a few weeks ago that the idea had backing from a wide range of countries in the 47-nation council -- including members of the self-styled non-aligned group (NAM), who normally unite to shield each other from criticism.

Earlier that same week, Swedish state secretary for foreign affairs Frank Belfrage told the five-year-old rights body his country was deeply concerned by "the worsening human rights situation in Iran."

He said the number of executions in Iran so far this year had reaching alarming proportions. "The most horrendous methods of killing human beings are still being used. Taking a person's life by stoning them is nothing less than barbaric," he added.

U.S. Secretary of State Hillary Clinton told the council that Iran pursued "violence abroad and tyranny at home." Iranian rights activists wanted a UN investigator, she added.

"The resolution that is being pursued has a lot of support from across the regions because Iran is an extreme case," Donahoe said, adding that the U.S. would be "working with Sweden very hard on this."

UN rights chief Navi Pillay says there has been a wave of arrests of opponents and critics of the Iranian government, apparently prompted by popular uprisings in nearby Arab states.

Based on the proposal, a post of special rapporteur, or investigator, will be created to monitor Iran's compliance with international rights agreements it has signed and to report regularly to the council.

Co-sponsors of the resolution include the Maldives, an Indian ocean archipelago which is a member with Iran of the 57-nation Organization of Islamic States (OIC), and Zambia, part of the African group, Donahoe said.

OIC and African countries are part of the wider -- and majority -- NAM bloc in the council, as well as in the UN General Assembly, which, with the support of Russia, China and Cuba, can usually control its agenda.