A new video posted on the Internet Tuesday, appearing to show the beheading of Steven Sotloff, a second captive American journalist, by the Islamic militant group, local media reported.

According to reports, in the video posted online yesterday, Sotloff addresses the camera, saying, "I am sure you know exactly who I am by now and why I am appearing."

The video then cut to the militant who said as long as U.S. missiles "continue to strike our people, our knife will continue to strike the necks of your people," said the reports.

Bernadette Meehan, a spokesperson for the White House National Security Council, said the U.S. intelligence community was working "as quickly as possible to determine" the video's authenticity.