Secret footage obtained by Channel 4 News revealed harrowing images of patients who were allegedly tortured by medical staff at a state-run hospital in Homs.
The video has intensified pressure on Western leaders to act against President Assad amid fears of an acute humanitarian and human rights crisis.
UN humanitarian affairs chief Valerie Amos has now said that the Syrian government has agreed to allow her to visit the country later this week.
She is expected to be in Syria from Wednesday to Friday. Syrian state media said that she will meet the Syrian foreign minister and the head of Syria’s Red Crescent.
Although it also said she would visit several areas in Syria, it is as yet unclear as to whether she will be granted the unhindered access she is demanding.
“As requested by the secretary general [Ban Ki-moon], my aim is to urge all parties to allow unhindered access for humanitarian relief workers so tha they can evacuate the wounded and deliver essential supplies,” she said.
The decision to allow Ms Amos into the country follows a rebuke of Damascus by the UN Security Council last week for failing to grant the humanitarian chief access to Syrian conflict zones.
Kofi Annan, the UN-Arab League special envoy to Syria, is expected to travel to Damascus on Saturday for his first visit since taking up the post.
Meanwhile, hundreds of Syrians have crossed over the border into Lebanon over the past day to escape the heaviest shelling of their border towns since the uprising against President Assad began last March.
Between 100 to 150 families arrived at the hillside town of Arsal, in Lebanon’s Bekaa Valley, from Syria on Sunday, as families trekked on foot to safety through snow-capped hills.
US Senator, John McCain, has lent his voice to the clamour calling for action against Syria. He has said the US should lead an international effort to protect key population centres in Syria through air strikes on President Assad’s forces.