Over 20,000 Syrian refugees have entered northern Iraq since Thursday in one of the largest crossings in the more than two-year-old conflict and the influx is continuing, the United Nations said on Monday.

Syrians began pouring into the Kurdistan region of northern Iraq last Thursday, taking advantage of a new bridge along the largely closed border, the UN says.

"It looks like the total from last Thursday to now is somewhere in the region of 20,000 or more coming across," Adrian Edwards of the UN refugee agency UNHCR said. "If not the biggest influx across the border at a single time then it is among the largest in the whole Syria crisis."

Hundreds of Syrians fleeing fighting in Aleppo and other parts of northern Syria were massed along the Tigris River on Monday near the pontoon crossing, UNHCR staff said. - Reuters