UN humanitarian chief Valerie Amos and UN human rights commissioner Navi Pillay said in a joint appeal on Saturday, “We understand there may also be as many as 1,500 wounded people in urgent need of immediate evacuation for emergency medical treatment, and that the general situation in al-Qusayr is desperate.”

They also said there were reports that civilian neighborhoods continued to be indiscriminately attacked and that other major violations of human rights and international humanitarian law were being committed.

The two called for an “immediate ceasefire” to allow an evacuation of the wounded by humanitarian agencies.

Meanwhile, UN Secretary General Ban Ki-moon demanded that Syrian government soldiers and the militants let the trapped civilians escape the town, which have been at the center of a raging battle for more than two weeks now.

“He urges all sides to do their utmost to avoid civilian casualties,” UN spokesman Martin Nesirky said in a statement, warning that they would be “held accountable for any acts of atrocity carried out against the civilian population of Qusayr.”

Hundreds of militants have reportedly arrived in Qusayr to counter the Syrian government forces, who backed by civilian fighters, have made major gains in the fighting.

For both sides, winning control of Qusayr will be a turning point in the war as the town sits on the route between Damascus and the coast, providing a key supply route for the militants.