Nearly 800,000 Afghan migrants returned or were deported back to Afghanistan from Iran in 2018 -- an increase of two-thirds compared to the previous year, the International Organization for Migration (IOM) said on January 8.
Laurence Hart, the chief of the IOM mission to Afghanistan, said the trend was accelerated by the renewed U.S. sanctions on Iran which sent the Iranian currency into freefall and fueled inflation.
Hart, speaking in the Afghan city of Herat, said the trend was expected to continue.
"The reason why people are coming back is because of the reduced economic opportunities in the region...including Iran," Hart said.
The 2018 figure was the highest since the IOM began recording the number of returnees to Afghanistan in 2012.
Meanwhile, just under 33,000 Afghans came back from Pakistan, where many have lived since fleeing the 1979 Soviet invasion.
An estimated 1.5-2 million "undocumented" Afghans are in Iran, the United Nations' refugee agency said in September, citing government estimates.
Another 1 million are registered as refugees.
For years, desperate Afghans have been paying smugglers $300-500 per person to cross the border with Iran in search of work to support struggling families.
Iran's rial lost around half its value against the dollar last year after U.S. President Donald Trump pulled out of the 2015 nuclear deal and reimposed tough sanctions on Tehran.
Meanwhile, a group of 36 rejected Afghan asylum seekers deported from Germany landed in Kabul on January 8.
A total of 475 Afghan men have been sent back from Germany since 2016.
In July, an Afghan killed himself after being deported. The 23-year-old had lived in Germany for eight years before he was sent back to Kabul.