MarineTraffic.com data showed the MT Hankuk Chemi leaving Bandar Abbas in the early morning hours. South Korea's Foreign Ministry said Iran released the tanker and its captain after seizing the vessel in January. The ministry says the Hankuk Chemi left an Iranian port at around 6 a.m. local time after completing an administrative process.

Iran did not immediately acknowledge the ship had been freed. The ship's owner, DM Shipping Co. Ltd. of Busan, South Korea, could not be immediately reached for comment.

The Hankuk Chemi had been traveling from a petrochemicals facility in Jubail, Saudi Arabia, to Fujairah in the United Arab Emirates when armed Revolutionary Guard troops stormed the vessel in January and forced the ship to change course and travel to Iran. Iran had accused the MT Hankuk Chemi of polluting the waters in the crucial Strait of Hormuz. But the seizure was widely seen as an attempt to pressure Seoul to release billions of dollars in Iranian assets tied up in South Korean banks amid heavy American sanctions on Iran. South Korea's Foreign Ministry did not elaborate on the terms of the ship's release. Iran in February released much of the ship's crew.

South Korea's Yonhap news agency, quoting an anonymous Foreign Ministry official, suggested Seoul may pay off Iran's United Nations dues that had been in arrears. In January, the UN said Iran topped a list of countries owing money to the world body with a minimum bill of over $16 million. If unpaid, Iran could lose its voting rights as required under the UN Charter.

"We're expecting to make considerable progress in terms of paying the UN dues," the official said. "We have also exported some $30 million worth of medical equipment since we resumed the humanitarian trade with Iran last April." The development came as Iran and world powers were set to resume negotiations in Vienna on Friday to break the standoff over US sanctions against Iran and Iranian breaches of the nuclear agreement. The 2015 nuclear accord, which then-President Donald Trump abandoned three years later, offered Iran sanctions relief in exchange for restrictions on its nuclear program.