Thousands of Koreans were evacuated as Typhoon Hinnamur made landfall in the south of the country, expecting heavy rain and strong winds to continue throughout the day, the authorities in South Korea announced on Tuesday.

Super Typhoon Hinnamnor made landfall on South Korea's Geoje early Tuesday morning, possibly becoming the most powerful storm ever to hit the country.

The strength of the typhoon when it hit Geoje was not immediately available, but the Korea Meteorological Administration (KMA) said the typhoon was classified "very strong" when it passed through the southern island of Jeju at around midnight with an atmospheric pressure of 945 hectopascals (hPa) at its center and maximum wind speed of 45 kilometers per second.

"Hinnamnor is a very big typhoon with a radius of 400 kilometers, and can carry strong winds and heavy rainfall almost all across the country," Han Sang-un, the chief forecaster at the KMA, told a press briefing, urging to minimize possible casualties.

After brushing past Jeju, Typhoon Hinnamnor was forecast to pass 180 kilometers southwest of the southern port city of Busan, with an atmospheric pressure of 945hPa at its center, the KMA said earlier.

A heavy rain warning was issued earlier for all parts of the country, but the warning has been lifted in areas including the western port city of Incheon after the typhoon moved past Jeju and continued to move eastward.

Almost all schools in Jeju were closed. Nationwide, 62 elementary, middle and high schools temporarily closed down, 548 schools switched to online learning. A series of ferry services and flights were canceled across the country.

Across the country, a total of 361 domestic flights had been cancelled as of Monday afternoon. (QNA)