A South Korean delegation is in Pyongyang to take part in four-day joint May Day celebrations involving workers of the two Koreas.

The 310-member South Korean delegation, comprised of representatives from the South's two umbrella labor unions, left Incheon International Airport earlier in the day on a direct charter flight to Pyongyang.

The delegates will attend the main May Day ceremony on Saturday and also visit historical sites, subway stations and production facilities in Pyongyang.

The delegation will also deliver 100 thousand dollars worth of relief aid packages for victims of a deadly train blast in the city of Ryongchon last week.

Additionally, the delegates are to discuss relief plans with their North Korean counterparts for the swift reconstruction of the city, much of which was leveled by the massive explosion.