BEIRUT: Three Syrian opposition factions have agreed a cease-fire in southern Damascus under an deal brokered by Egypt and Russia that was not signed by the Syrian government, officials said Thursday.

The deal did not specify the area, but the three rebel groups control a pocket south of Damascus adjacent to areas controlled by Daesh (ISIS). The deal would allow for humanitarian access but, unlike other similar agreements, would not involve the relocation of militants or residents.

Several such deals in recent years have involved bussing tens of thousands of people to the rebel-held Idlib province, in northwestern Syria. The opposition has accused the government of forced displacement, charges denied by Syrian officials.

Egypt’s state-run MENA news agency said the deal did not include the Syrian government. Russia has been a main backer of President Bashar Assad’s government, while Egypt has maintained intelligence and security cooperation with the government since 2013.

“The residents of this area will stay in their homes and this [deal] will lift the siege and cease the fire,” Mohammad Alloush, of the Army of Islam rebel group, said by telephone. He confirmed that the Army of Islam, Jaysh al-Ababil and Aknaf Beit al-Maqdis, which is linked to the Palestinian Hamas group, were part of the agreement.

MENA said the deal was signed at the intelligence headquarters in Cairo early Thursday and went into effect at noon.

It said the crossings south of Damascus would remain open for humanitarian access, adding that other opposition factions have been invited to join the cease-fire.

The deal came as Syrian opposition activists said government troops are pushing deeper into a Daesh stronghold in the country’s east, the town of Mayadeen in Deir al-Zor province.

The Britain-based Syrian Observatory for Human Rights said clashes intensified early Thursday, as government forces advanced into the western and northern neighborhoods of Mayadeen, which lies on the Euphrates River.

The Observatory said troops were able to cut off the road linking Mayadeen and the town of Boukamal on the border with Iraq. It added that Daesh brought in reinforcements from Iraq and elsewhere in Syria.

Opposition activist Mozahem al-Salloum said the fighting is fierce “in a way not seen before.”

Omar Abu Laila, who runs a group that monitors developments in Deir al-Zor, said it will likely take time to drive Daesh out of Mayadeen, which is one of its last major strongholds.

Syrian troops reached Mayadeen Saturday, after pushing south along the eastern banks of the Euphrates.

The U.N. children’s agency said fighting related to the Mayadeen offensive has destroyed at least 140,000 doses of vaccines.

The report, which UNICEF regional director Geert Cappelaere said the agency is working to verify, is “alarming” and is likely to hamper an ongoing vaccination drive in the area.

The agency said Mayadeen has been at the center of an outbreak of polio caused by vaccine shortages.

Since March, 48 children have been paralyzed in the area, according to UNICEF.

UNICEF didn’t say what caused the destruction of the cold room where the vaccines were stored. A government offensive in the area has displaced most of the town’s population. The agency says the vaccines were to be used for an ongoing campaign in the surrounding Deir al-Zor province, where children have been “extremely vulnerable” to the spread of the illness.

UNICEF says this is the second outbreak of polio in Syria since the start of the civil war in 2011. National vaccination coverage has dropped from over 80 percent to just over 40 percent.