DAMASCUS  - Syrian rebels claimed they downed a fighter jet Monday in what would be a major coup for the opposition but the regime seized the upper hand in Aleppo as it advanced into a new rebel-held district.

Government forces also bombarded areas around Damascus and launched a wide sweep of the capital, including its once-bustling historic Old City, while shocking videos emerged showing alleged rebel atrocities in the Aleppo area.

A group of rebels said they have captured the pilot of a warplane that the Free Syrian Army claimed to have shot down on Monday in the far east of the country.

The man, identified as pilot Colonel Mufid Mohammed Sleiman, was described as “a staunch enemy of the revolution” by the FSA spokesman, who said he had served with him for years before his own defection.

A video distributed by the “Revolutionary Youth of the Land of the Euphrates” after the rebels claimed to have shot down a Russian-made MiG fighter near Muhasen in Deir Ezzor province shows Sleiman surrounded by three armed men.

Syria’s state media said earlier that a warplane had suffered a malfunction while on a routine training mission in the province and that the pilot had ejected.

Another group calling itself the “Revolutionary Youth of the Land of the Euphrates” distributed a video showing a man identified as pilot Mufid Mohammed Suleiman, surrounded by three armed men.

“My mission was to bomb the town of Muhasen,” said the purported pilot.

At least 90 lost their lives on Monday, according to the Syrian Observatory for Human Rights. The opposition has accused the regime of increasingly resorting to firing from fighter planes, particularly on the second city of Aleppo which has witnessed some of the fiercest fighting in recent weeks.

Meanwhile, grisly footage of apparent atrocities in the Aleppo area emerged, appearing to show rebels callously throwing bodies off a post office building.

The latest to flee Monday was Syria’s top representative at the UNHRC. 

Also Monday, security forces arrested 22 residents in a major security sweep in the heart of Damascus, including the Old City, while shells slammed into rebel strongholds around the capital, according to the Observatory.

It was biggest operation of its kind in Damascus since the launch of the uprising, the Observatory said.

China said that a top aide to Bashar al-Assad will visit this week for talks with Chinese leaders, as violence rages in the country.

Bouthaina Shaaban, a “special adviser” to the Syrian president, will visit from Tuesday for talks with Chinese Foreign Minister Yang Jiechi and other officials, the foreign ministry said in a statement. China was also considering inviting members of the Syrian opposition to visit soon, it said, but gave no details.