Jordanian fighter jets struck Islamic State targets for a third straight day Saturday, as the militants' claim that a Jordanian airstrike killed an American hostage remained unconfirmed.
Jordan launched the raids to avenge the killing of a Jordanian pilot the Islamic State group captured in Syria in December.
The United Arab Emirates said Saturday that it ordered a squadron of F-16 fighter planes to Jordan to help with the airstrikes. State news agency WAM carried the announcement.
Both Jordan and the UAE are members of the U.S.-led coalition attacking the militants in their captured territory in Iraq and Syria. Coalition airstrikes also continued Saturday, as the fate of the American aid worker being held by Islamic State remained unknown.
Kayla Mueller's family released a statement Friday, saying they remained hopeful she still is alive. Carl and Marsha Mueller asked the captors of their 26-year-old daughter to "respond to us privately.”
Their response came after the White House on Friday said it had seen no evidence to corroborate the militants' claim of her death.
Skepticism over the claim comes after Jordanian authorities said fighter pilot Muath al-Kaseasbeh was killed in early January, a month before the Islamic State released a video showing his death.
Mueller is the last remaining U.S. hostage known to be in the hands of the Islamic State group. Three other Americans held by the militants were beheaded.
Jordanian officials called Islamic State's report of Mueller's death "criminal propaganda." Foreign Minister Nasser Judeh said on Twitter that it is "an old and sick trick used by terrorists and despots for decades — claiming that hostage human shields held captive are killed by air raids."
Mueller reportedly moved by suffering
Those who know Mueller say she was deeply moved by the suffering of civilians stuck in poverty and caught up in war and terrorism. She had worked in Syria and volunteered with aid groups in the West Bank and India. Militants kidnapped her in 2013 as she was leaving a hospital in Aleppo.
The Islamic State said she was killed when a Jordanian airstrike hit the building where she was being held in the Syrian city of Raqqa.
Meanwhile, Jordan's King Abdullah has vowed an "earth-shaking," open-ended response to Kaseasbeh's killing.
An Islamic State video posted online Tuesday showed the pilot locked in a cage, soaked with gasoline and burned alive while armed fighters watched.
Demonstration in Amman
Thousands of people flooded the streets of Amman Friday in support of Kaseasbeh. The demonstrators marched through the Jordanian capital after Friday prayers, waving flags and chanting slogans against the militants. Jordan's Queen Rania joined the marchers and held up a picture of the murdered pilot.
Jordan said its recent airstrikes against Islamic State targets are only the beginning of its retaliation for the killing.