Thousands of Syrians on Thursday poured into northern Iraq through a new bridge along the largely closed border, a UN spokesman said here on Friday. Field officers with the UN High Commissioner for Refugees described waves of people \"streaming\" over the recently constructed bridge at Peshkhabour into Iraq\'s Kurdistan region in a sudden and massive movement, said Eduardo del Buey, deputy spokesperson for UN secretary-general, at a daily briefing. \"The first group of Syrians, some 750 people, crossed over the pontoon bridge at Peshkhabour at the Tigris River before noon,\" del Buey said. \"Later in the afternoon, a much larger group of 5,000 to 7,000 people followed.\" The vast majority of the new arrivals are women, children and elderly persons, mainly from Aleppo, Efrin, Hassake, Qamishly and other embattled areas of Syria, where fighting has intensified between government forces and the opposition. More buses were seen dropping off people on the Syrian side, and some people have reportedly encamped near the Tigris River for two to three days, the spokesman said. The UN refugee agency also said both the Syrian and Iraqi sides of the frontier at the Peshkhabour crossing are normally tightly controlled and the factors allowing this sudden movement are not fully clear at this stage. As of Friday, nearly 2 million Syrians have fled the war and registered as refugees or applied for registration, two-thirds of whom arrived this year, del Buey said. And according to a search of shelter, an average of 6,000 Syrians a day leave their motherland in this year. There are now more than 684,000 Syrian refugees in Lebanon, 516,000 in Jordan, 434,000 in Turkey, 154,000 in Iraq (not including the latest arrivals) and 107,000 in Egypt, the spokesman added. In July, the UN said that the Syrian civil war has led to the worst refugee crisis since 1994. On Friday, Syrian warplanes struck targets in a rebel-held district in the northern city of Aleppo, killing at least 15 people and wounding dozens of others. As the war continues, the refugee crisis is expected to worsen. The UN estimated that there could be 3.5 million Syrian refugees by the end of 2013, more than half of whom will be children.