MIAMI (AFP) - Flags will fly half-mast on Friday in the US state of Florida, where the family of beheaded US journalist Steven Sotloff lives, its governor said.

Sotloff, 31, was beheaded by Islamic State militants in a video released on Tuesday, two weeks after the similar video of US journalist James Foley was posted online.

"In honour and in memory of Steven Sotloff, I hereby direct the flags of the United States and the state of Florida to be flown at half-staff at all local and state buildings, installations, and grounds throughout the state of Florida," Governor Rick Scott said in a statement.

Sotloff was kidnapped on April 4, 2013 in Aleppo near the Turkish border, but his abduction was kept secret after his family requested a media blackout.

His family on Wednesday paid tribute to the slain journalist, remembering him as a thoughtful man who enjoyed simple pleasures and was fascinated by the Middle East.

He was a freelance reporter who had written for Time magazine, Foreign Policy and other outlets. He was born in Miami.