(CNN) -- Syria's nearly 3-year-old civil war saw more bloodshed Thursday, and perhaps a moment of peace.
Fighting at a huge prison in the volatile city of Aleppo brought conflicting rebel claims on whether they controlled all or part of the facility.
Meanwhile, the United Nations and the United States confirmed an agreement announced by rebels and the government of a planned cease-fire in the besieged Old City of Homs that would allow some people to flee and humanitarian aid to arrive for the first time in over a year.
"We welcome the news that a deal has been reached," U.S. State Department spokeswoman Jen Psaki said of what she called "a local humanitarian pause" to begin Friday.
An opposition spokesman in Homs, Abu Rami, said the agreement called for a cease-fire at a time to be set by the government and expected imminently.
Once the fighting halts, women, civilians over 55 and children under 15 can choose to leave the Old City if they agree not to take up arms against the government, he said.
After the first group of evacuations, Syrian troops would clear the way for a U.N. aid convoy packed with food and medicine to enter the area for the first time in more than a year, according to Abu Rami.
"We have nothing to give the families," he told CNN via Skype from the Old City of Homs. "We are crippled because of the lack of food and medicine, which especially affects the women, children, and the elderly, so for the sake of the public good, we must agree to this cease-fire."
According to SANA, the official Syrian news agency, the government would provide shelter, food and medical treatment to people who leave the Old City. In addition, the agreement calls for government forces to allow humanitarian assistance to people who remain in the besieged area, SANA reported.
Valerie Amos, the U.N. emergency relief coordinator, said the cease-fire agreement would mean essential supplies for about 2,500 people in Homs.
"What we're waiting for is a green light to be given by the parties for safe passage," said Farhan Haq, a spokesman for U.N. Secretary-General Ban Ki-moon.
In Washington, Psaki called on Syrian President Bashar al-Assad's government to follow through on allowing U.N. convoys to enter Homs, adding that "an evacuation is not a substitute for the safe, regular, and unfettered delivery of humanitarian assistance to those in need wherever they are."
"We should not be giving credit to a regime just for providing food for a few days to people who are starving, given that's the right moral thing to do, and this is something they should have been doing all along," Psaki said.
Asked about concerns that the Syrian regime might be preparing for a final assault on those who remain in Homs once the other civilians depart, Psaki refused to speculate but said it was important for the U.N. convoys to get access to the Old City.
In Aleppo, Islamist brigade Ahrar al-Sham and al Qaeda-linked al-Nusra Front took control of the sprawling six-story Aleppo Central Prison from government forces after announcing an offensive to free detainees, opposition groups the Aleppo Media Center and Syrian Observatory for Human Rights said Thursday.
However, an activist from the rebel Shahba Press Agency group, Nazeer al-Khatib, later told CNN only a part of the prison was under rebel control. He cited miscommunication for backtracking on the initial claims.
"Information came from the Ahrar al-Sham media office regarding the full takeover of the prison and media activists hurried the transmission of information," al-Khatib told CNN via Skype from the city.
The media center and the observatory could not be immediately reached for comment.
Aleppo is a major battle front in the Syrian conflict, which has killed more than 100,000 people and displaced millions since erupting in 2011.
The prison has an estimated 3,000 detainees, many of them prisoners of conscience. At least 800 women were among the prisoners, al-Khatib told CNN.
Clashes between government forces and rebels started early Thursday after rebels detonated a car bomb in front of a building in the prison complex housing Syrian army troops, the Aleppo Media Center said.
Government warplanes dropped barrel bombs on the perimeter of the prison and tanks fired shells to reverse the advance of insurgents, causing dozens of casualties, the Syrian Observatory for Human Rights said.
CNN's Joe Sterling and Tom Cohen contributed to this report.