Thousands of Syrian refugees poured into the Kurdistan region of northern Iraq on Thursday, taking advantage of a new bridge along the largely closed border, the United Nations said on Friday.

Between 5,000 and 7,000 refugees followed a first group of some 750 people who crossed the pontoon bridge at Peshkhabour over the Tigris River, and more buses were seen dropping off families on the Syrian side, it said.

"Thousands of Syrians crossed into northern Iraq yesterday (Thursday) in a sudden, massive movement," Adrian Edwards, spokesman of the UN High Commissioner for Refugees (UNHCR), told a news briefing in Geneva.

Most were families with women, children and the elderly, mainly from Aleppo, Hassakeh and other embattled areas of Syria where fighting has intensified in the civil war, now in its third year, that has driven nearly 2 million refugees abroad.

There are already more than 150,000 Syrian refugees registered in Iraq, according to the UNHCR which has urged all neighboring countries to keep open their borders to Syrians needing international protection.

The border between Syria and Iraq has been largely closed since authorities of the Kurdish regional government shut the crossing on May 19, apart from a single formal crossing point at Al-Wahid in Anbar province.

Some Syrian refugees had been allowed in since mid-July for reasons of family reunification or dire humanitarian need, Edwards added.

Asked about growing insecurity in Iraq after a surge in sectarian violence, he said: "Kurdistan remains relatively safe and stable; however tensions are increasing in view of the forthcoming elections and also to do with other domestic factors there.

"This does have impact on our (aid) delivery program in Iraq, but nonetheless it is the region where most refugees have come into."

Overall the flow of Syrian refugees has dropped sharply since a peak earlier this year when 5,000 to 8,000 crossed every day into neighboring countries, according to the UNHCR.

The agency is also monitoring the turmoil in Egypt, where there are 107,000 Syrian registered refugees, although the government estimates that the true number is closer to a quarter of a million, Edwards said.

"It is a difficult situation for them at the moment; they of course are not alone in having difficulties in Egypt right now. We are looking at protection needs and trying to do what we can in the current very difficult situation for everyone," he said.