Attempts to evacuate two wounded journalists from the besieged city of Homs failed again on Monday night as ambulances carrying injured civilians left without them.
Sunday Times photographer Paul Conroy and French reporter Edith Bouvier, of Le Figaro newspaper, were injured in a deadly bombardment which killed war correspondent Marie Colvin and French photojournalist Remi Ochlik on Wednesday.
Teams from the Syrian Arab Red Crescent made their way into the embattled neighbourhood of Baba Amr today to remove casualties but parted without the wounded journalists or the bodies of their colleagues.
A spokesman for the International Committee of the Red Cross (ICRC) said: "We were not able to evacuate the foreign journalists or the bodies of those journalists killed last week.
"We do not know the reason why.
"The situation on the ground is very tense and communications are very difficult."
The ambulances left Baba Amr, which has been devastated by a month of shelling by Syrian government forces, carrying an elderly woman and a pregnant woman with her husband.
Efforts to rescue Mr Conroy and Ms Bouvier were launched last week following the rocket attack on the makeshift media centre where they were working.
On Sunday, Mr Conroy's wife Kate said her husband had rejected an opportunity to leave Homs with the Syrian Arab Red Crescent for fear it was "not to be trusted", the Press Association reported.
International Development Secretary Andrew Mitchell has said there was evidence of people on the ground "infiltrating" the humanitarian organisation and "posing an additional danger" to anyone seeking to leave the city.
Foreign Office officials are understood to be working alongside the French embassy to try to retrieve the journalists and are said to be pressing the Syrian ministry of foreign affairs.
Mr Conroy, 47, from Totnes, Devon, has appealed for help in a video posted on YouTube.
Lying on a sofa in a darkened room and covered in a blanket, he said he sustained "three large wounds" to his leg in the attack and was being looked after by the Free Syrian Army medical staff.
The freelance photographer and film-maker, who was also hit in the stomach by shrapnel, added that he wanted to reassure family and friends in Britain that he was "absolutely OK".
Ms Bouvier, who suffered multiple leg fractures, was also seen begging for help in being evacuated to safety in Lebanon.
On Friday, teams from the ICRC were deployed to Homs to evacuate seven wounded and 20 women and children.
The organisation has since stressed the "urgent" need to evacuate those who require help and bring in vital assistance.
The Foreign Office has said "all the necessary work" was being done to repatriate Ms Colvin's body and ensure Mr Conroy "gets to safety".
The award-winning war reporter, 56, was killed after defying an order from her editor to leave the opposition stronghold of Homs because she wanted to finish "one more story", her mother Rosemarie has said.
At the time, she was the only British newspaper reporter in the city, which has become a symbol of the 11-month uprising against Syrian president Bashar Assad.
Syrian activists have accused his forces of deliberately targeting the journalists.
The Syrian foreign ministry has offered condolences to the families of Ms Colvin and Mr Ochlik but denied any responsibility for their deaths.