Islamic State (IS) militants claim that a US female hostage has been killed in a Jordanian air strike in Syria.
IS named the woman as aid worker Kayla Jean Mueller in statements posted online.
The group provided no other proof for the claim beyond pictures of the alleged site of the air strike, in Raqqa, the group's stronghold in Syria.
The White House said it was "deeply concerned" by the reports but that it has yet to verify them.
Ms Mueller was working with Syrian refugees when she was kidnapped in 2013.
'Upping the ante'
Jordan said it carried out aerial bombardments on IS targets in Syria, including on Raqqa.
Local activists and IS sympathisers reported fresh strikes in the city on Friday, but these have not been confirmed by officials.
The strikes were carried out in response to the killing of a Jordanian fighter pilot by IS militants.
A video of Moaz al-Kasasbeh being burned alive in a cage was posted online by IS earlier this week.
He was captured by militants in December after his F-16 fighter jet crashed in Syria. The video is believed to have been filmed on 3 January.
Foreign Minister Nasser Judeh said Thursday's strikes were "the beginning of our retaliation" against IS.
"We're upping the ante. We're going after them wherever they are, with everything that we have," he said.
Thousands rallied in Jordan's capital, Amman, on Friday morning in support of their government's military response.
Among those marching was Jordan's Queen Rania who told the BBC the country was "united in our horror".
She said Lt Kasasbeh's killing had made Jordanians "determined to rid the world of this evil".