The United Nations Security Council has demanded that UN humanitarian chief Valerie Amos be allowed "immediate and unhindered access" to Syria by the government there, amid a heavy government assault on a restive city.
Thursday's press statement was supported by Russia and China, which had previously blocked stronger resolutions on Syria. It came as government ground troops reportedly entered the Bab Amr district of Homs, where armed rebels have held out under a month of bomardment.
Mark Lyall Grant, the United Kingdom's UN ambassador, read out the statement and cited concern over the "growing number of affected civilians, the lack of safe access to adequate medical services, and food shortages, particularly in areas affected by fighting and violence such as Homs, Hama, Deraa and Idlib".
Amos' request to visit Syria has been rejected by the government, which said the proposed date was not suitable.
Council diplomats said Russia, Syria's closest ally, had urged Assad's government to approve a visit by Amos. In a concession to Russia and China, the statement called on the government and opposition to co-operate with efforts to evacuate the wounded from Syrian cities.
Earlier, the two nations - joined by Cuba - voted against a UN Human Rights Council resolution that condemned Syria for "widespread and systematic violations" against civilians.
The resolution also supported gathering evidence on possible crimes against humanity and other serious abuses, so that those who are responsible can be held to account at a later date.
The United Nations has estimated that more than 7,500 people have been killed since the anti-Assad struggle started in March 2011, when protesters took to the streets in Syria.
On Thursday evening, rebels and activists reported that the armed opposition, the "Free Syrian Army" had withdrawn from Bab Amr in a "tactical retreat". The fighters said they were running out of weapons and wanted to spare some 4,000 remaining civilians from more violence.
They said the district was running out of food, medicine and water and was suffering communication cuts.
Homs is Syria's third-largest city and before the uprising began was home to about one million people. Bab Amr had roughly 100,000 residents, but many have fled.
The withdrawal came after the last remaining foreign journalists in Homs were smuggled safely to Lebanon. French journalists Edith Bouvier and William Daniels, on assignment for the Figaro newspaper, were both injured in a February 22 artillery strike on a makeshift media centre in Bab Amr.
Spanish journalist Javier Espinosa and British photographer Paul Conroy, who was also injured in the attack, escaped to Lebanon on Wednesday.
US reporter Marie Colvin and French photographer Remi Ochlik were both killed by the same shelling, and activists in Homs said they were both buried on Thursday after it was decided that there was not enough fuel to continue refridgerating their bodies indefinitely.