About a thousand of South Korean protesters held an anti-North Korea rally as North Korean leader Kim Jong Un invited South Korea’s President Moon Jae-in to Pyongyang.

North Korean leader’s sister Kim Yo Jong, who is visiting South Korea to attend the Pyeongchang Winter Olympics, delivered her brother’s personal invitation during a meeting with moon, Seoul’s presidential spokesman said.

Police estimated that about 1,300 protesters gathered in front of Dongdaemun design plaza and they burnt a unified peninsula flag, which was used by north and South Korean athletes when they marched together at the opening ceremony of Pyeongchang Winter Olympics.

The “Korean unification flag,” showing the Korean peninsula in blue against a white background, traces its origin to 1989, when North and South Korea agreed to use a new flag for a possible joint team in the 1990 Asian Games.