LONDON Two Reuters journalists are missing in Syria.
Diplomatic sources said on Wednesday that correspondent Suleiman al-Khalidi, a Jordanian national based in Amman, had been detained by the Syrian authorities in Damascus on Tuesday.
Photographer Khaled al-Hariri, a Syrian based in Damascus, has not been in contact with colleagues since Monday.
A Syrian official said authorities were working to establish what had happened to the two men.
"Thomson Reuters is deeply concerned about the whereabouts of our colleagues Khaled al-Hariri and Suleiman al-Khalidi," Reuters Editor-in-Chief Stephen Adler said.
"We call upon the Syrian authorities to help us urgently in ensuring their safe and timely release. Reuters remains committed to reporting from the Middle East and we are working round the clock to protect our staff in these challenging times."
Khalidi, who has worked for Reuters for more than 20 years in Jordan, Kuwait, Syria and Iraq, was last seen in the old city of Damascus on Tuesday. He has not answered his mobile telephone since shortly after 2 p.m. (1200 GMT) on Tuesday.
Hariri, who has also worked for Reuters for more than 20 years, was last seen arriving at the Reuters bureau in Damascus on Monday morning. He has not been in touch since then and has not answered his mobile telephone.
Their disappearance follows the detention in Syria of two Reuters television journalists, producer Ayat Basma and cameraman Ezzat Baltaji. They were held incommunicado for two days before being released by Syrian authorities on Monday.
Both Lebanese, they were expelled to Lebanon. They had been working in Syria since the previous week.
Reuters correspondent Khaled Yacoub Oweis, a Jordanian who had been based in Damascus, was expelled from Syria on Friday for what a Syrian Information Ministry official described as his "unprofessional and false" coverage of events.
Reuters said it stood by its coverage from Syria, where nearly two weeks of protests have posed the biggest challenge to President Bashar al-Assad's 11-year rule.
Also on Wednesday, the Libyan government expelled a Reuters correspondent from Tripoli. Two weeks ago, Saudi Arabia expelled the Reuters foreign correspondent from Riyadh.
(Reporting by Dominic Evans, editing by Alastair Macdonald)