An annual mass migration started in South Korea on Thursday as people headed to their hometowns for one of the country's key traditional holidays.

Seol, or Lunar New Year's Day, falls on Saturday this year, with the official holiday period running from Friday to Monday.

Along with Chuseok, the equivalent of Thanksgiving in the United States, Seol marks South Korea's longest holiday in which many South Koreans head back to their hometowns to pay homage to their ancestors and spend time with family and friends.

People streamed into the main train station in central Seoul, as well as the city's express bus terminals, that link the capital to regional cities and towns across the country.

Some 220,000 vehicles have left the capital area as of 2 p.m., according to Korea Expressway Corp. (KEC). Another 230,000 cars are expected to be added to the number by midnight.

"The number will reach its peak at around 6 to 7 p.m. when most travelers hit the road after quitting time," a KEC official said. 

Others headed to airports to go abroad for Lunar New Year or to tourist destinations in the country.

"Instead of holding the ancestral rites, we are going to the resort island of Jeju for three days," Kim Jae-kwan, 77, told Yonhap News Agency at Gimpo International Airport, west of Seoul.

Kim said a total of 15 family members, including his son and daughter, are going on the trip.

The state-run Korea Transport Institute forecast that as many as 31.15 million people will travel to their hometowns or tourist sites nationwide during the holiday period. (Yonhap)