BEIRUT: Two abandoned patients fled a bombed-out mental hospital in Syria's northern city of Aleppo this week and were killed by snipers, activists said, highlighting the horror of a conflict which the UN says has killed 60,000 people.

The men were gunned down by sniper fire on Wednesday in the embattled city where fighting has been at a grinding stalemate for months, the Britain-based Syrian Observatory for Human Rights activist said.

Both the Observatory and local residents reported that other mentally ill people had been found wandering the streets over the past week, and identified them as former patients of the Ibn Khaldun psychiatric hospital east of the city.

Its location alongside Nayrab military airbase and the adjacent Aleppo international airport meant Ibn Khaldun was severely damaged by shelling on December 23 as battles raged between troops and rebels, the Observatory said.

A video posted to YouTube by activists on December 25 shows sunlight pouring inside the hospital through gaping holes in its walls and shattered windows, chairs overturned and rooms empty.

One doctor told AFP that the administration had issued an appeal in late December for relatives of the patients to come and take them away because of deteriorating security.

The Dar al-Ajaza psychiatric hospital in the Old City has also faced army bombardment and chronic shortages of food since fighting broke out in July, but it remains in operation thanks to dedicated staff and its central location.

To reach Ibn Khaldun from Aleppo city, however, requires a trip along the perilous airport road, where fighting rages unabated between rebels and troops.

The doctor admitted that neither he nor the colleagues he spoke to had been willing to risk their own safety and travel to work for more than a week, leaving some 100 patients to their own fate.

In a video posted to YouTube on New Year's Day, a man is shown visiting the hospital and speaking about the conditions inside.

"This place is not hygienic. There's no food, no water inside. We are going to bring them what they need," the visitor said, attaching a padlock to the gate as he prepared to leave.

Some dozen patients clamoured at the entrance.

"We have been bombed... We have no basics, no food, electricity, nothing," one cried.

The same visitor was seen in another video posted on Tuesday, entitled "The reason for moving the patients at Ibn Khaldun hospital."

"Because of the shelling on the hospital, a lot of staff and patients fled. We have taken them to a safe place where we will provide everything for them," a man said, introducing himself as a member of the society for Promotion of Virtue and Aid to the Oppressed.

The camera panned to show basic meals of sandwiches and water being assembled for the patients in a spotless room.

The doctor confirmed that the patients have been transferred to a benevolent society in the northeastern district of Masaken Hanano, but warned that they were still at risk.

"This charity was not prepared to receive mentally ill patients and cannot provide the necessary care or guards. There have been repeated cases of patients fleeing," he said.

Masaken Hanano residents said the patients had been breaking out of the charity for the past week and roaming the streets.

"Every time they escape we take them back," Abdel Hamid, a local plumber, told AFP.

But in the midst of a brutal war that has left the country's once thriving commercial hub bereft of electricity, bread and security, this may be the best the local people can do.

The director of Ibn Khaldun hospital was not available for comment because of severed communications in the city.