Syrian rebel fighters and Assad-regime forces fought what the opposition Free Syrian Army called a decisive battle for the northwestern city of Aleppo Friday. The fighting came a day after the bloodiest day of Syria's 18-month revolt, with at least 343 people killed, an opposition watchdog group said. Six-thousand fighters of the Tawhid Brigade, supported by other armed groups, fought regime forces in Syria's largest city, brigade Cmdr. Bashir al-Haji told British newspaper The Guardian. The battle, which Haji said started Thursday afternoon, does not seek "to liberate the whole of Aleppo ... but to regain control of most of the city and get back as many neighborhoods as we can," he told the newspaper by Skype over sounds of shellfire. "We only need anti-aircraft rockets to control the way from Aleppo to Damascus," about 190 miles south, he said. Haji denied the FSA had proclaimed "decisive" battles for Aleppo before. FSA is the shorthand phrase for army defectors, volunteers and religious militants who make up the anti-Assad forces. The Tawhid Brigade's founder, who uses the pseudonym Abu Khalid, is a jihadist who was jailed several times in Syria, McClatchy Newspapers reported. The state-run Syrian Arab News Agency, monitored by United Press International, did not immediately report on the Aleppo fighting. The reports could not be independently verified. The fighting followed the deadliest day of the Syrian conflict as at least 343 people were killed, including 107 people allegedly massacred in a Damascus suburb, the Local Coordination Committees reported. The previous highest daily death toll was July 19, when 302 people were killed, the British-based Syrian Observatory for Human Rights reported.