Trees are uprooted by heavy rain and strong winds in the country's largest port city of Busan, Sept. 6. Yonhap

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

The typhoon, the 11th this year, made landfall at the southeastern city of Geoje, South Gyeongsang Province at 4:50 a.m., according to the Korea Meteorological Administration (KMA). Geoje city is made up of a number of islands, of which by far the largest is Geoje Island.

The strength of the typhoon when it hit Geoje was not immediately available, but the 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.

Typhoons are classified into four categories: medium, strong, very strong and super strong. Super strong refers to typhoons with a maximum wind speed of at least 54 meters per second.

After brushing past Jeju, Typhoon Hinnamnor was forecast to pass 180 kilometers southwest of the southern port city of Busan by 3 a.m., with an atmospheric pressure of 945hPa at its center, the KMA said earlier.

Waves hit a seawall in Busan on Sept. 6, as the super strong Typhoon Hinnamnor approaches the Korean Peninsula. Yonhap

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.