Britain's Foreign Secretary William Hague and
Britain's Foreign Secretary William Hague andReuters

United Nations Secretary-General Ban Ki-moon on Friday said he was “deeply” concerned about reports of the possible use of chemical weapons by Syria, and demanded the government state it would not use them “under any circumstances.”

“I remain deeply concerned about the reports of the possible use of chemical weapons,” Ban was quoted by Reuters as having told reporters, citing one report in which Syria said it would use such weapons if it was attacked by foreign powers.

“I demand .... that the Syrian authorities categorically state that they will not use chemical or other weapons of mass destruction under any circumstances,” he added, speaking at a joint news conference in London with British Foreign Secretary William Hague.

Both Hague and Ban expressed deep concern about escalating violence in the Syrian city of Aleppo, which is under a major assault by government forces.

“I also want them to know in the Assad regime that the more they do this sort of thing, the more we will increase the practical support we give to the opposition movements in Syria,” Hague said, referring to Syrian President Bashar al-Assad.

Meanwhile, Reuters reported on Friday that rebels have detained scores of Syrian officers, soldiers and pro-government militiamen this week in Idlib province and in the city of Aleppo, where a major battle is anticipated.

A video posted on YouTube showed rebels with Kalashnikovs in Aleppo from "The Tawheed (monotheism) Brigade" guarding the detainees who were lined up in four groups on a school playground. An off-camera voice said they had been detained in Aleppo, Syria's biggest city.

Some of the detainees' faces were covered with bruises and showed signs of swelling around their eyes and when they spoke their voices quavered.

One said he was a colonel, another a major and several identified themselves as shabbiha, a term used by opposition to describe militiamen who are loyal to Assad and are fighting alongside his troops.

At the end of the video, a rebel voice said: "The Free Army will terminate all the shabbiha.” A rebel from the group told Reuters that the detainees were safe and have been moved to an unidentified site in the countryside around Aleppo, which is a rebel stronghold.