The head of Syrian Air Force intelligence was reportedly assassinated in Damascus Saturday, rebels said, as the war-town country devolved into one of its bloodiest periods yet, with over 500 people reported killed, including 370 in one town.

A spokesperson for the Free Syrian Army told al-Arabiya on Sunday that Lt. Jamil Hassan was killed in his office by an aide, who was an operative for Ahfad al-Rasul (Grandchildren of the Prophet Brigade), a group that operates under the aegis of the Free Syrian Army and has claimed credit for bombings in the past.

Damascus denied the report.

Hassan was reportedly targeted due to the recent escalating Syrian Air Force bombardment of rebel groups and neighborhoods.

He was considered a close adviser of Syrian President Bashar Assad.

Opposition forces have reported assassinations in the past that were later disputed, including of Assad’s brother Maher and a top Russian general.

Also Saturday, rebel activists reported upwards of 400 people were killed in Syria over the day, including a massacre in a Sunni town south of the capital.

A local activist in the town of Daraya told Reuters that 200 bodies had been found there, most of them shot execution-style. Later reports said 370 bodies had been found

“In the last hour, 122 bodies were discovered and it appears that two dozen died from sniper fire and the rest were summarily executed by gunshots from close range,” the activist told Reuters by telephone.

He called what happened “a massacre.”

The Local Coordination Committees reported that over 300 people had been killed in and around Damascus and hundreds more in fighting in other places around the country, including Aleppo, Daraa and Deir Al Zour in the north of the country. Some estimates but the death toll at over 500 people.

State-run media reported government forces “cleared the area of terrorists,” their term for the rebels, “and eliminated a large number of them.”

Video from the town posted on YouTube showed scores of bodies with gunshot wounds lying in a dark room. Warning: graphic footage

Another video from the town purported to show forces loyal to Assad beating bound rebels.

Damascus itself also saw heavy fighting on Saturday, as tanks shelled rebel-held neighborhoods in the south of the city, Reuters reported.

On Friday, Damascus residents reported hearing loud explosions as shells fired from the Qasioun mountains overlooking the capital slammed into Daraya and the nearby suburb of Moadimiyeh.

Human rights groups say more than 20,000 people have been killed in Syria since the uprising against Assad erupted in March 2011 and evolved into a civil war. The bloodshed already has spilled over into neighboring countries.

On Friday, the United Nation’s refugee body reported that the number of people fleeing the country had surpassed 200,000, as thousands headed for safe havens in Turkey and Jordan.