The Syrian government blocked a Red Cross convoy from delivering badly needed food, medical supplies and blankets to a rebellious neighborhood of Homs, cut off by a month-long siege.
On Friday, activists accused regime troops who overran the shattered district of execution-style killings and a scorched-earth campaign.
- Syria threatens to crush rebels in Homs
UK withdraws diplomats from Syria
Syrian rebel connects with IDF spokesman on Facebook
Humanitarian conditions in the former rebel stronghold of Baba Amr have been described as catastrophic, with extended power outages, shortages of food and water, and no medical care for the sick and wounded.
British Prime Minister David Cameron called Homs "a scene of medieval barbarity."
Syrian government forces took control of Baba Amr on Thursday after rebels fled the district under constant bombardment that activists said killed hundreds of people since early February. The Syrian regime has said it was fighting "armed gangs" in Baba Amr, and had vowed to "cleanse" the neighborhood.
"It is unacceptable that people who have been in need of emergency assistance for weeks have still not received any help," said Jakob Kellenberger, president of the International Committee of the Red Cross.
'It's not a war, it's a massacre.' Paul Conroy
The Red Cross said it had received permission from the government of President Bashar Assad on Thursday to enter Baba Amr, on the western side of Homs, and a convoy of seven trucks with 15 tons of humanitarian aid was poised to do so, but authorities then blocked their access.
There was no explanation from the government about the change. "We are staying in Homs tonight in the hope of entering Baba Amr in the very near future," Kellenberger said.
UN Secretary-General Ban Ki-moon called on Syria to give humanitarian workers immediate access to people who desperately need aid.
"The images which we have seen in Syria are atrocious," said Ban. "It's totally unacceptable, intolerable. How, as a human being, can you bear this situation?"
Homs (Photo: AFP/YouTube)
UN Humanitarian Chief Valerie Amos has been trying, without success, to get permission from the Syrian government to visit, and Ban said Assad's regime should let her into the country to assess the situation without delay.
British photographer Paul Conroy, who was wounded by shelling in Baba Amr and trapped there for several days until he escaped, told Britain's Sky News that "It's not a war. It's a massacre – indiscriminate massacre of men, women and children."
The European Union committed itself to document war crimes in Syria to set the stage for a "day of reckoning" for the country's leadership, in the way that former Yugoslav leaders were tried for war crimes in the 1990s by a special UN tribunal.
EU leaders in Brussels condemned Assad's regime for its nearly yearlong crackdown on an uprising that began with mostly peaceful protests but has veered toward civil war, with Syrian forces firing heavy artillery against civilians.
The UN has estimated that more than 7,500 people have been killed, while activists put the death toll at over 8,000.
Reuters and AFP contributed to this report
- Receive Ynetnews updates
directly to your desktop