Up to 5,000 Afghan refugees a day are crossing into neighboring Iran, which already faces a heavy burden hosting an estimated 3.6 million Afghans, a relief group said Wednesday.

The Norwegian Refugee Council called for more international support for Iran which, despite facing tough US economic sanctions, operates what the council described as one of the most inclusive refugee policies in the world. 

"Iran cannot be expected to host so many Afghans with so little support from the international community," the Council's Secretary-General Jan Egeland said after a visit to Iran this week.

He stressed that "there must be an immediate scale-up of aid both inside Afghanistan and in neighboring countries like Iran, before the deadly winter cold."

The council said it was estimated that at least 300,000 Afghans had crossed into Iran since the Taliban entered Kabul coinciding with the withdrawal of US forces, following a 20-year presence.

It added that around $136 million of a $300 million appeal launched by the UN refugee agency to help up to 515,000 people who may flee Afghanistan before the end of the year was earmarked for Iran. 

"Now the international community must step up to support Afghanistan's neighbors and share the responsibility to help them to continue welcoming refugees," Egeland affirmed.

For his part, Iranian Minister of Interior Ahmad Vahidi expressed on Tuesday his country's fear that the number of new refugees would reach about one million.

In a meeting organized by the judicial authority with representatives of diplomatic missions in Tehran, Vahidi explained that when the Afghan economy collapses and Afghans don't receive assistance, they will head to the border with Iran.

The Iranian Interior Minister expressed that his country respects and cherishes refugees, but their numbers are huge.

He added that the 3.5 million Afghans in Iran benefit from the same financial aid that Iranians receive.