The International Organization for Migration said migrants in Iran were highly vulnerable amid heavy bombardment and mass displacement, lacking support structures relied on by Iranian nationals.

The United Nations agency said it "stands ready to support migrants and other third-country nationals caught in the crisis".

"We have already assisted some migrants to return home from Iran," David John, IOM's director of resettlement and movement management, told reporters in Geneva.

"The requests now are in the hundreds (and) the number is increasing by the day," he said, without providing details on the nationalities assisted or requesting help.

John said assistance requests from migrants' home countries could soon be "in the thousands".

Since erupting on February 28 with US-Israeli attacks on Iran, the war has cascaded throughout the region, drawn in global powers, and sparked a major oil shock.

UNHCR, the UN refugee agency, said Thursday that as many as 3.2 million people had been displaced in Iran.

Some were refugee families who were "particularly vulnerable, given their already precarious situation and limited support networks".

Iran is the largest refugee-hosting country globally, and it counts a large migrant population, including millions of Afghans and hundreds of thousands of Iraqis, according to the UN.

- Safe repatriation options needed -

John stressed that the main barrier to evacuation assistance by IOM was "resources".

"We remain confident in our ability to facilitate the repatriation and evacuation of migrants, if we have the resources to do so," he said.

He highlighted that "these evacuation operations are costly", adding that for the agency to help evacuate 200 people, "you're looking at a neighbourhood of somewhere around $600,000-$700,000".

Migrant workers have reportedly already figured among the civilian casualties in Iran, Salvador Gutierrez, the IOM's chief of mission in Iran, said in a statement.

This, he said, underscored "the urgency of providing safe and organised repatriation options".

The IOM said had also been approached by some embassies in Lebanon, which has been heavily impacted by the war, enquiring about help evacuating their nationals.

"At this stage, it's very much to help to prepare for possibly evacuation, rather than direct requests yet for evacuations," Mathieu Luciano, IOM's chief of mission in Lebanon, told reporters in Geneva, speaking from Beirut.

The conflict has heavily impacted Lebanon, where authorities reported 687 people killed by Israeli attacks, while more than 800,000 people have been displaced.

Luciano said the IOM estimated that "at least 30,000 migrants are now displaced", out of the around 200,000 who live in Lebanon.

UNHCR said more than 94,000 Syrians living in Lebanon had crossed over into Syria, along with 10,000 Lebanese.