Several thousand Syrian rebels launched Thursday what they said would be a decisive battle for control of the strategic northern city of Aleppo as the Syrian government warned it was “game over.” “Tonight, Aleppo will be ours or we will be defeated,” Abu Furat, a rebel commander said. As they announced the preparations, Syrian authorities sent text messages over cellphones nationwide with a message for rebels fighting President Bashar Assad’s regime: “Game over.” The messages signed by the Syrian Arab Army also urged the rebels to surrender their weapons and warned that the countdown to evict foreign fighters had begun. The battle cries came a day after rebels bombed a military command center in Damascus and after more than 300 people were killed nationwide Wednesday in what the opposition Syrian Observatory for Human Rights said was the bloodiest day of the 18-month conflict so far. An AFP correspondent saw dozens of rebels grouping in Aleppo’s northern Izaa quarter and firing mortars as they spoke to other groups by walkie-talkie. In a video posted on YouTube in the name of the most important rebel unit, the Al-Tawhid Brigade, a man in civilian clothing clutching a walkie-talkie is seen giving instructions. “Today the attack against Bashar’s army began on all fronts,” he says, referring to Assad’s forces. “God willing, today’s battle in Aleppo will be decisive.” “Don’t kill any prisoners,” he orders. “Disarm them and hand them over to the security committee of the revolution. Each man to his post.” The Observatory reported fierce combat in the early evening in the districts of Izaa and Saif al-Dawla in the southwest, involving “hundreds of rebel fighters.” Aleppo has seen raging clashes since July, when rebels launched an offensive to capture the commercial capital. After some early successes, the rebel campaign slowed because of a shortage of ammunition. At least seven civilians were killed Thursday in the northern metropolis as troops pummeled districts across the southwest and the east, the Britain-based Observatory said. The violence came after a car bomb exploded at an army checkpoint overnight in the northwest province of Idlib, about 25 kilometers south of Aleppo on the highway to Damascus. Rebels then attacked the checkpoint and fierce clashes raged, the Observatory said. In what appeared to be the same attack, a military source said clashes erupted overnight at a checkpoint in the same area after a minibus exploded. “When we saw the bus with just one driver and no one else in it, we thought it was suspicious and told him to stop.” “He didn’t and when we shot the driver the bus veered off the road and exploded,” the source told AFP. A large rebel force then attacked the checkpoint, said the source, who added that the fighting lasted until 7:30 am when the rebels withdrew. The Observatory also reported that unidentified attackers blew up an oil pipeline in the northeast province of Hasaka, Syria’s main oil-producing region. In Idlib province, five civilians, including four children, died in army bombardment of Khan Sheikhun, according to the Observatory. Activist footage posted on YouTube showed pandemonium in the town, as men formed lines in a race to move chunks of rubble and the crowd began shouting as a small limp girl was lifted up and handed to a grey-haired man. The authenticity of the video could not be verified independently. At least 59 people – 38 civilians, 16 soldiers and five rebels – were killed nationwide Thursday, according to an early toll from the Observatory. Rebels and government aligned forces are now locked in a stalemate after 18 months of conflict. Activists say the death toll since the uprising against Assad began in March last year has topped 30,000, with nearly two-thirds of the casualties reported in the past five months. International diplomacy has failed to end the crisis. World leaders meeting at the United Nations this week expressed concern at the violence but are deadlocked over their response to the conflict. Qatar, one of several Sunni Muslim powers which supports the rebels, called for a no-fly zone to provide a safe haven inside Syria. French President Francois Hollande also called on the global body to protect what he called “liberated zones” under rebel control. But there is little chance of securing a Security Council mandate for such action given the opposition of veto-wielding members Russia and China. Turkish Prime Minister Recep Tayyip Erdogan said Thursday that Russia, China and Iran’s stance on Syria was letting a massacre go on unabated. “The main source of disappointment is Russia. Let alone raising its voice against Syria, it stands by the massacre,” Erdogan said in an interview broadcast live on Turkish television station NTV. “China stands by Russia, and although [Chinese President] Hu Jintao had told me they wouldn’t veto the plan [for a safe zone] for a third time, they did at the U.N. vote,” Erdogan said. He described Iran’s position on the 18-month-old uprising against Assad as “impossible to understand.” “Assad’s days are numbered,” Erdogan said. “He may have to leave soon, he can’t resist this anymore.”