(CNN) A Saudi Arabian tugboat was seized by Yemen's Iranian-backed Houthi rebels on Sunday, according to the state-run Saudi Press Agency SPA.

The vessel was towing a South Korean drilling rig in the south of the Red Sea when it "fell under hijacking and armed robbery by two boats," Saudi military spokesman Colonel Turki al-Malki told a news conference, SPA reported. He did not say how many crew members were aboard the ship.

The Saudi ship was reportedly among three vessels seized within 3 miles (4.8 km) off Uqban island and taken to the Salif port in western Yemen, according to the Houthi-run Al-Masirah news agency. Al-Masirah did not report on the origin of the other two ships.

Two South Koreans were among those captured, Kim In-chul, a spokesman for South Korea's Ministry of Foreign Affairs confirmed on Tuesday.

"The South Korean nationals on the captive ships are safe and healthy and their families have been notified." Kim said.

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