An Islamic State video has appeared which purports to show the beheading of American journalist Steven Sotloff.
Sotloff, 31, disappeared in Syria in 2013. He appeared at the end of a video last month which showed fellow US journalist James Foley being killed.
After Foley's death, Sotloff's mother appealed to IS leader Abu Bakr al-Baghdadi to save her son's life, the BBC reports.
White House spokesman Josh Earnest said United States officials were checking the reports.
The US has recently carried out dozens of air strikes against IS targets in Iraq.