WASHINGTON (AFP) - A journalists' group called on the United States on Saturday to explore alternatives to military action in dealing with hostage-takings, after an American and a South African were killed in a failed rescue attempt in Yemen.

Luke Somers, an American photojournalist, and Pierre Korkie, a teacher, were killed early on Saturday in the unsuccessful rescue operation in Yemen's southeastern Shabwa province.

Reporters Without Borders said tragic outcomes in hostage-takings by Islamic extremists have become more and more frequent, underscoring the growing dangers facing journalists.

"We again urge the US government, which has announced its intention to review its policy on hostages, to explore all alternatives to the military option and to make every effort to guarantee the safety of the civilians involved," said Christophe Deloire, the secretary-general of Reporters Without Borders.

"This review must be conducted on the basis of consultation with former hostages, both US and foreign, with the families, if they so wish, and with the employers and NGOs concerned."

The charity group Gift of the Givers said it had been negotiating to secure Korkie's release and had expected him to go free as early as Saturday when the rescue operation intervened.

US President Barack Obama said he authorised the operation because of indications that Somers was in imminent danger.

In a video this week, Al-Qaeda in the Arabian Peninsula threatened to execute Somers within 72 hours.

Somers, who was kidnapped in September 2013, was the third American journalist killed this year in hostage-takings by Islamic extremists.

Two US journalists, James Foley and Steven Sotloff, American aid worker Peter Kassig and British aid workers Alan Henning and David Haines were all beheaded in Syria by the Islamic State group.