A man walks at Ganjali Khan historical bazaar in Kerman, Iran, Jan. 2, 2021. (Photo by Ahmad Halabisaz/Xinhua)

Iran said Tuesday it has allowed all crew except the captain from a South Korean tanker seized in January for alleged pollution to leave the country in a "humanitarian move."

The Islamic Revolutionary Guard Corps seized the Hankuk Chemi and arrested its multinational crew of 20 sailors near the strategic Strait of Hormuz on January 4, saying it had polluted the waters.

The development came as Tehran urged Seoul to release billions of dollars of Iranian assets frozen in South Korea due to US sanctions.

"In a humanitarian move by Iran, the crew of the South Korean tanker accused of polluting the environment of the Persian Gulf were allowed to leave the country," foreign ministry spokesman Saeed Khatibzadeh said in a statement.

Permission had been granted upon "the request of the South Korean government and [with] the cooperation of the judiciary in Iran," he added.

He did not specify whether the crew had already left.

Seoul-based news agency Yonhap cited the South Korean foreign ministry as saying the captain would remain in Iran to look after the tanker. It was not clear when the vessel might be allowed to leave.

The arrested crew were from South Korea, Indonesia, Vietnam, and Myanmar.

Former US president Donald Trump in 2018 withdrew Washington from a landmark nuclear agreement with world powers and then reimposed and reinforced crippling sanctions on Iran.

Iran was a key oil supplier to resource-poor South Korea until Washington's rules blocked the purchases.

According to government spokesman Ali Rabiei, Iran has $7 billion of funds blocked in Seoul.

The money can neither be transferred nor earn interest, yet Iran is charged fees on it, he has said.

AFP