The U.N. Security Council called Friday for Yemen's president to immediately accept a deal to transfer power to his deputy and end escalating violence in the strategically located Middle East nation.

The council unanimously adopted a resolution expressing serious concern at the worsening security and deteriorating economic and humanitarian situation in Yemen "due to the lack of progress on a political settlement and the potential for the further escalation of violence."

President Ali Abdullah Saleh has so far balked at a U.S.-backed plan proposed by Saudi Arabia and its five smaller allies in the Gulf Cooperation Council to hand over power to his deputy and step down in exchange for immunity. He is accused by many Yemenis of pushing the country toward civil war by clinging to power despite massive protests, the defection to the opposition of key tribal and military allies, and mounting international pressure to step down.

The resolution was the first adopted by the U.N.'s most powerful body since the Arab Spring uprising in Yemen began eight months ago. It was clearly aimed at stepping up international pressure on Saleh, who was president of North Yemen from 1978 until 1990 when he became the first president of a unified Yemen.

Yemeni activist Tawakul Karman, who was awarded the Nobel Peace Prize along with two Liberian women earlier this month, welcomed the resolution but said it didn't go far enough.

"We are asking for a trial" for Saleh, Karman told reporters at U.N. headquarters. "We are asking to send him to the international tribunal as a war criminal."

Philippe Bolopion, U.N. director for Human Rights Watch, said the organization welcomed "the long overdue condemnation of Yemeni government abuses," but believed the council should have distanced itself from the council's impunity deal.

"By signaling that there would be no consequence for the killing of Yemenis, the immunity deal has contributed to prolonging the bloodshed," he said.

British Ambassador Mark Lyall Grant was pleased with the unanimous approval of the resolution, which he said "includes some tough messages to President Saleh and to the opposition."

The resolution calls for Saleh, or those authorized to act on his behalf, to immediately sign the Gulf Cooperation Council deal "to achieve a peaceful political transition of power ... without further delay."

Although the deal would give Saleh immunity, the resolution also underlines the need for an independent investigation into alleged human rights abuses "with a view to avoiding impunity."

Saleh was gravely wounded in an explosion at his presidential palace in June and went to Saudi Arabia for treatment. During his absence, mediators and opposition groups sought to persuade him to stay away and transfer power, but he declined and returned abruptly to Yemen late last month.

Unlike the resolution on Syria that was vetoed by Russia and China on Oct. 4, the Yemen resolution makes no mention of sanctions or any other measures.

It demands "that all sides immediately reject the use of violence to achieve political goals," and that armed groups remove all weapons from areas where peaceful demonstrations are taking place.

The resolution "strongly condemns" human rights violations by Yemeni authorities including the excessive use of force against peaceful protesters.

With fighting intensifying, there are concerns that a civil war would significantly hurt efforts by the United States and Saudi Arabia to fight Yemen's dangerous al-Qaida branch, and could turn the mountainous nation into a global haven for militants a short distance away from the vast oil fields of the Gulf and the key shipping lanes in the Arabian and Red seas.

The resolution raises fresh concerns "at the increased threat from al-Qaida in the Arabian Peninsula and the risk of new terror attacks in parts of Yemen."

Al-Qaida in the Arabian Peninsula, as the Yemeni branch is known, is considered by the U.S. to be the most dangerous of the terror network's affiliates after it plotted two recent failed attacks on American soil.

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Associated Press Writer Anita Snow contributed to this report from the United Nations.