The Americans, both 31-year-old men, were seized on Wednesday while driving near the resort of Dahab.

"The tourists are with Egyptian security now," a security source told Reuters. "They were released after successful negotiations with the army, with the mediation of Bedouin sheikhs."

The U.S. embassy said earlier on Thursday it was working closely with the Egyptian authorities to resolve the situation.

Several other tourists have been held briefly by tribesmen in recent months and have also been released unharmed.

"We have been seeing repeated harassment by the police and sometimes the army lately. People had had enough and took the two tourists," said Sheikh Ahmed Hussein, a tribal leader from South Sinai.

He said the tribesman arrested by the authorities had been released and was returning to his family.

Bedouin have attacked police stations, blocked access to towns and taken hostages to show their discontent with what they see as their poor treatment by Cairo and to press for the release of jailed kinsmen.

Tribes in the south deny any link to ultra-conservative Islamist groups who are challenging state security for control of the north of the isolated peninsula.

Two American women were kidnapped in the area in February but Egyptian authorities negotiated their release a few hours later.

(Reporting by Youssri Mohamed and Tamim Elyan; Writing by Tamim Elyan; editing by Tim Pearce)

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