South Korea's deputy foreign minister met his Iranian counterpart in Tehran on Sunday, state news agency IRNA reported, days after Iran seized a South Korean-flagged tanker in sensitive Gulf waters.

Choi Jong-kun's meeting with Abbas Araghchi came after Iran's Revolutionary Guard said on Monday they had seized the South Korean-flagged Hankuk Chemi in Gulf waters.

The Guard cited the ship's "repeated infringement of maritime environmental laws".

South Korean news outlet Yonhap has said Choi's aim during his visit was to "negotiate an early release" of the tanker and its crew, which includes South Korean, Indonesian, Vietnamese and Burmese sailors.

But Iran's foreign ministry spokesman Said Khatibzadeh has said the visit was agreed before the tanker was seized, and that its "main goal" was "to discuss ways of accessing Iranian funds in [South] Korea".

Iran's seizure of the tanker came after Tehran had urged Seoul to release billions of dollars of Iranian assets frozen in South Korea under US sanctions.

The Islamic republic says it is struggling to buy vaccines to tackle its spiralling novel coronavirus caseload as well as medicines or medical equipment from abroad.

Choi was quoted by Yonhap on Sunday as saying that the visit "will be a good opportunity to clearly hear once again what the Iranian government wants and to distinguish what [we] can do and cannot do regarding the issue, as well as what needs to be consulted on with the US".

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