Up to 700,000 refugees may flee Syria by the end of the year, the U.N. refugee agency said on Thursday, escaping a conflict which is killing hundreds every day and dividing world powers meeting at the United Nations. The UNHCR forecast is almost four times higher than its June prediction, reflecting spiralling violence in Syria where President Bashar al-Assad has responded to rebel military gains with air strikes and artillery bombardment. Activists said more than 300 people were killed in Syria on Wednesday including dozens in a town southeast of Damascus where they accused Assad\'s forces of committing a massacre. Rebels also bombed the military staff headquarters in the capital. Around 294,000 refugees escaping 18 months of conflict have crossed into neighbouring Jordan, Iraq, Lebanon and Turkey, most of them in the last two months. \"This is a significant outflow taking place, 100,000 people in August, 60,000 in September and at the moment 2,000 or 3,000 per day or night,\" Panos Moumtzis, Regional Refugee Coordinator for UNHCR, said in Geneva. The flow of refugees surged in August when Assad deployed jets and helicopters to strike rebel-held towns in the northern provinces of Aleppo and Idlib, sending thousands across the border with Turkey. Heavy military clashes with rebels in Deraa in the south also drove many Syrians into neighbouring Jordan. U.N. aid agencies and humanitarian partners issued a funding appeal on Thursday for $488 million to try to help meet the needs of the rapidly growing number of refugees from Syria. Since the uprising against Assad erupted in March last year, more than 30,000 people have been killed, the Syrian Observatory for Human Rights said this week. It said more than 7,000 of those were soldiers and members of the security forces. The United Nations says many more have been displaced and that 2.5 million people in the country need aid and assistance. \"STAIN ON U.N.\" World leaders meeting at the United Nations have expressed concern at the continuing violence but are deadlocked over their response to the conflict, which pits mainly Sunni Muslim rebels against Assad, who is from an Alawite minority close to Shi\'ite Islam. 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 United Nations to protect what he called \"liberated zones\" under rebel control. But Western powers have shied away from supplying military aid to rebels who include foreign jihadists and there is little chance of securing a Security Council mandate for such action given the opposition of veto-wielding members Russia and China. Russian President Vladimir Putin said in Moscow on Wednesday any attempt to use force unilaterally or interfere with events in the Middle East would be counterproductive. China\'s Foreign Minister Yang Jiechi said the destiny of the region \"should be held in the hands of its own people\". Egypt\'s Islamist President Mohamed Mursi, who last month called on the world to stand against Assad\'s \"oppressive regime\", said his country opposed foreign military intervention to halt the fighting. Citing a report by a rights group about violence against Syrian children, British Prime Minister David Cameron said the violence was a \"stain on the reputation of this United Nations\" and on countries which \"failed to stand up to these atrocities and in some cases aided and abetted Assad\'s regime of terror.\" Wednesday\'s death toll of over 300 - reported by the British-based Syrian Observatory for Human Rights and the opposition Local Coordination Committees - made it one of the bloodiest of the 18-month-old uprising. The Observatory, which monitors violence in Syria through a network of activists, said that 55 people had been killed in rural areas around Damascus. They included at least 40 who appeared to have been executed in the town of al-Dhiyabia, southeast of the capital. Other activists put the death toll in al-Dhiyabia as high as 107, blaming Assad\'s security forces for what they said was a massacre. Video published by activists showed rows of bloodied corpses wrapped in blankets. The victims shown on camera appeared to be males - from 20-year-olds to elderly men. Some had gunshot wounds in the forehead, face or neck. The Observatory also said 14 people had been killed in a rebel bomb attack on a military command centre in Damascus and in an ensuing prolonged gun battle between rebels and members of the security forces. Violence in Syria has deepened as the struggle against Assad has became more militarised and the president has responded with increasing force. In the first nine months of the conflict, the United Nations human rights chief said around 5,000 people had been killed. U.N. officials have given up trying to monitor the violence but the Observatory\'s figures suggest five times as many people have been killed in the second nine-month period.