(ATTN: CLARIFIES headline, lead; ADDS more details in paras 4-9, 15)
SEOUL, Jan. 5 (Yonhap) -- South Korea's anti-piracy unit began operations in waters near the Strait of Hormuz on Tuesday to respond to heightened tensions after Iran's seizure of a South Korean oil tanker, officials said.
On Monday, Iran's Islamic Revolution Guards Corps seized the tanker, the MT Hankuk Chemi, due to what Teheran claims to be environmental and chemical pollution by the ship.
The vessel, which was traveling from Saudi Arabia to the United Arab Emirates, was carrying 20 crew members -- five South Koreans, 11 Myanmarese, two Indonesians and two Vietnamese.
"The Cheonghae Unit arrived in waters near the Hormuz Strait earlier in the day. It is carrying out missions to ensure the safety of our nationals," ministry spokesperson Boo Seung-chan told a regular briefing.
The ministry refused to give details, but officials stressed that the unit is not taking military actions for the release.
"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," another official said.
Around six South Korean vessels are known to sail through the waterway every day.
South Korea has also been in close coordination with multinational entities operating in nearby waters, the official added.
The 33rd contingent of the 300-strong Cheonghae Unit on the 4,400-ton destroyer Choi Young has been in the Middle Eastern region since late last year to conduct anti-piracy missions.
Foreign Minister Kang Kyung-wha said that South Korea is making diplomatic efforts for the swift release of the ship and crewmembers.
"We have been trying to figure out what happened through the Iranian Embassy in South Korea and the South Korean Embassy in Iran and continuing to make efforts to address this situation," Kang told reporters.
Asked about speculation that Tehran might have seized the ship out of anger over its assets frozen in Korea due to U.S. sanctions, Kang stressed the first priority is on "verifying the facts and ensuring the safety of the crewmembers."
On Monday, the U.S. State Department called on Iran to immediately release the tanker, saying that the seizure is part of Teheran's attempt to press the international community into lifting sanctions on the country.
As the world's most important oil passageway and a chokepoint between the Arabian Gulf and the Gulf of Oman, the strait is the route to the open ocean for more than one-sixth of global oil production and 70 percent of South Korea's oil imports.
The Cheonghae Unit has been in the Gulf of Aden off Somalia since 2009 and broadened its mission areas into the Gulf of Oman and the Persian Gulf last year amid heightening tensions in the region.
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