Seoul's Defense Ministry said Tuesday a destroyer carrying members of South Korea's anti-piracy unit had arrived in waters near the Strait of Hormuz and was "carrying out a mission to ensure the safety of our nationals", without giving details.
Seoul said the 300-strong Cheonghae unit had been in the region since late last year and would not engage in an offensive operation, an unnamed military official told the South's Yonhap News Agency.
"The issue should be resolved through diplomacy. The unit is focused on the safety of our people who use the waterway after the seizure incident," they added, AFP reported.
Earlier, Foreign ministry spokesman Choi Young-sam said a government delegation would be "dispatched to Iran at the earliest possible date to try to resolve the matter through bilateral negotiations."
The arrested crew were from South Korea, Indonesia, Vietnam, and Myanmar, the Guards said on its website Sepahnews, without giving further details.
The seizure followed days of high US-Iran tensions marked by the first anniversary of the US assassination of Iran's revered military commander Major General Qasem Soleimani in a Baghdad drone strike.
The United States Sunday reversed a decision to bring the aircraft carrier USS Nimitz home from the Gulf, with the Pentagon citing "recent threats" by Iran.
Separately, South Korea's vice foreign minister Choi Jong-kun will go ahead with a planned three-day trip to Tehran early next week, the spokesman added.
The vice minister's visit had been arranged prior to the seizure, as Tehran seeks the release of billions of dollars held in Seoul under US sanctions.
According to Iran's central bank governor Abdolnasser Hemmati, the country has "$7 billion of deposits in South Korea" that can neither "be transferred nor do we get any returns on, while they ask us for the costs" of holding the funds.
South Korea's foreign minister Kang Kyung-wha did not comment on speculation that Iran seized the ship in a bid to pressure Seoul to unlock Iranian assets.
"We need to verify the facts first and ensure the safety of our crew," Kang told reporters.
"We are making diplomatic efforts for an early release," she added.
