GENEVA – The United Nations Thursday increased its funding appeal for Syrians who have fled the conflict in their country to almost $490 million, warning that the number of refugees could rise to over 700,000 by the end of the year. So far donors have given $141.5 million toward humanitarian assistance for the estimated 294,000 Syrians who have fled abroad, the UN refugee agency and 51 other aid groups said in a joint appeal. “We only have one-third of the funding we need to respond,” said Panos Moumtzis, Syria coordinator for the UN High Commissioner for Refugees. “We are running out of time and we need to respond.” Aid groups had previously estimated that 100,000 Syrians would have crossed into neighboring Jordan, Lebanon, Iraq and Turkey by the end of 2012. But with no end in sight to the 18-month conflict and 2,000 to 3,000 Syrians crossing daily into neighboring countries, humanitarian groups are preparing to help up to 710,000 by year end, said Moumtzis. This includes Syrians who have already fled abroad but have yet to come forward to register as refugees. Almost 95,000 Syrians have found refuge in Jordan, followed by almost 88,000 in Turkey and 78,000 in Lebanon. Some 33,000 Syrians have fled to Iraq, which recently reopened its border crossing at Al-Qaim. Meanwhile, a rights group said Thursday that more than 305 people were killed in the bloodiest day of Syria's 18-month revolt, as Washington urged action from the “paralyzed” UN Security Council. As fighting raged in several parts of Syria, unknown attackers blew up an oil pipeline in the northeast province of Hasaka, the Syrian Observatory for Human Rights reported. Wednesday was the deadliest day of the Syrian conflict as more than 305 people died across the country, including 14 in a twin bomb attack against the headquarters of the armed forces in the heart of Damascus, the Observatory said. It said 199 of Wednesday's dead were civilians. “This is the highest toll in a single day since March 2011. And this is only counting those whose names have been documented. If we count the unidentified bodies, the figure will be much higher,” said Observatory head Rami Abdel Rahman. The previous highest death toll of the uprising was on July 19, when 302 people were killed, according to the Britain-based watchdog. More than 30,000 people have been killed overall in violence since the March 2011 outbreak of the revolt against the rule of President Bashar Al-Assad, in a toll compiled by the Observatory. In Aleppo city, troops pummeled the southwest district of Kalasseh and the eastern district of Sakhur and nearby Suleiman Al-Halabi street, leaving an unknown number of casualties, said the Observatory. The violence followed a pre-dawn rebel attack on an army checkpoint in the northwest province of Idlib, about 25 km south of Aleppo on the highway to Damascus. Fighting was also reported in Homs, Hama city, the coastal province of Latakia and the eastern province of Deir Ezzor. At least five people were killed Thursday, including a child shot dead by a sniper in Hama city. – Agencies