In less than a week, some 20,000 Syrian refugees have left their homeland and fled to the Kurdistan region of northern Iraq, using a newly built bridge on the border to make the trip, according to the United Nations refugee agency.

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

It's unclear what exactly caused the massive influx of refugees, though fighting between Syrian Kurds and anti-government Islamist militants could be one of many contributing factors.

The Kurdish regional government and assisting NGOs are having a difficult time supporting the massive amount of people escaping Syria's civil war, many of whom come from Aleppo, Afrin, Hassake and Qamishli.

Astonishing UNHCR photo shows mass exodus of #Syria refugees fleeing to #Iraq on newly constructed pontoon bridge. pic.twitter.com/zaCs9wfO9p — Hala Gorani (@HalaGorani) August 19, 2013

About 150,000 refugees have already registered in Iraq, and more are expected to arrive. More than 1.9 million Syrians have left their home since the war began, many seeking refuge in neighboring Lebanon, Jordan or Turkey.

"UNHCR and partner agency teams, together with local authorities, worked into the early hours to aid the new arrivals," Edwards said.

This video from UNHCR documents the migration of refugees: