The United Nations said it has been guaranteed access to Misurata where the situation remains "dire" amid severe shortages of food, power, water and medicine in the face of intense shelling by forces loyal to Gaddafi.
Valerie Amos, the UN humanitarian chief, secured the deal through talks in Tripoli.
A Libyan official told Amos that Gaddafi's government was willing to set up "safe passage" out of the city, which remains partially under the control of the rebels after weeks of attacks by the army.
The Libyan authorities have promised aid workers and their equipment access to all areas under their control, BBC said.
However, the top UN official said she received "no guarantees" of a cessation of hostilities "to enable people to move" or for supplies to be delivered, Al Jazeera reported.
The deal was finalised after Amos apparently pledged to increase the UN presence in the capital in return for humanitarian access in other Libyan cities, it said.
The pan-Arab channel quoted witnesses as saying that the pro-Gaddafi forces pounded the port city with rockets and artillery today. The city, which was living under the threat of bombardment, was facing severe shortages of food, water, fuel and electricity.
At least 20 people died while queuing for bread when Grad rockets rained down on them, it said.
"There is no safe place left here," a Sudannese woman was quoted as saying.
Amid the fierce battle between Gaddafi's troops and rebels, nearly 1,000 foreign workers and wounded Libyans were evacuated from Misurata, the lone rebel bastion 214 kilometres east of the capital Tripoli that been under siege for over seven weeks.
"The ship docked in Benghazi straight from Misurata carrying 970 passengers on board," Al Jazeera said.
The International Organization for Migration (IOM) said at least 4,000 more are awaiting rescue and that the situation on the ground is getting increasingly difficult for further evacuation missions.
Britain's Department for International Development said approximately 300 civilians had been killed and a further 1,000 injured since late February in Misurata.
However, media reports said 1,000 people are estimated to have been died in the fighting in Misurata and "80 per cent of the deaths are civilians".
The Special Envoy of UN Secretary-General Ban Ki-moon to Libya, Abdul Ilah Al-Khatib and Amos, visited Tripoli on Sunday.
"I am encouraged to report that, as a result, the UN reached an agreement on a humanitarian presence in Tripoli," Ban told reporters yesterday in Budapest.
