File Photo: Children pose for photographs in front of their tents at a camp for internally displaced families in Panjwai District of Kandahar province, Afghanistan, on March 31, 2021. AFP
"We risk having an implosion that will cause an inflow of people inside the country for sure but at that point also outside of the country in quest of better conditions of life," Grandi told reporters via video link from Geneva.
The United Nations has repeatedly warned that Afghanistan is on the brink of the world's worst humanitarian crisis.
More than half of Afghanistan's 38 million population is expected to face hunger this winter, according to aid groups, as the economy teeters on the verge of collapse following the Taliban's return to power and as international aid remains frozen.
Grandi said that the crisis can still be avoided, but it requires faster action in terms of implementing systems to ensure the Afghan economy can function, that services continue and that cash flow into the country resumes.
He added that he will travel to Tehran in several days to discuss the issue with Iran's leaders.
Iran has been a leading destination for Afghan refugees fleeing war and economic troubles for decades.
Despite the risk of famine in Afghanistan, Iran has recently been expelling tens of thousands of Afghans every week, including those who had long been living there.
According to the UNHCR, there are 3.4 million Afghans in Iran, including nearly two million undocumented migrants and 800,000 refugees.
Furthermore, some 3.5 million Afghans have been displaced inside their country, many of them before the Taliban came to power in August, according to UN estimates.
Grandi would not say how many people have been displaced since the Taliban takeover and how many new refugees are expected because he didn't not have those numbers yet.