Syrian children inside a Jordanian refugee camp.
Syrian refugee children play at Al Zaatari refugee camp in the Jordanian city of Mafraq, near the border with Syria, Jan. 30, 2016. REUTERS/Muhammad Hamed

As many as 20,000 Syrian refugees are thought to be stranded on the war-torn country’s border with Jordan, the head of the U.N. refugee agency said in the kingdom Sunday. He also noted 4,000 to 5,000 were arriving in the rural desert region each month. So far, Jordan has permitted only a few dozen refugees to enter each day, meaning crowds of mostly women and children have begun to build.

The problem for Syrian authorities, they claim, is that many of the refugees came from regions controlled by the Islamic State group, meaning each person needs to be vetted before being allowed into the country.

In the meantime, international aid groups have asked Jordan to hurry before the humanitarian situation on the border becomes more difficult. Jordan hosts the U.N.-run Azraq refugee camp, which is only half full and could accommodate thousands more.

Jordanian officials were also asked by the U.N. to provide the “most basic necessities” to those still living on the border with Jordan given that the nearest town is 150 kilometers (90 miles) away, said Andrew Harper, the refugee agency chief in Jordan.

By current estimates, there are around 1.26 million Syrians living in Jordan, twice the number of registered Syrian refugees, said Qasem al-Zoubi, the head of the country’s statistics department. According to the country’s 2015 census, there are 9.5 million people living in Jordan, including 6.6 million Jordanians and 2.9 million noncitizens. Syrians make up the majority of noncitizens.

The data was released ahead of the annual Syria aid conference where Jordan will ask for more international help to deal with the current level of refugees in the country and those trying to enter after fleeing the five-year civil war.