SEOUL—South Korea's national anthem was broadcast and its national flag shown in North Korea for the first time at a weightlifting tournament on Saturday, the latest indication of gradually improving ties between Seoul and Pyongyang.

North Korean state media reported that South Korean athletes took gold and silver in an 85-kilogram (187-pound) division at a stadium in Pyongyang. At the medal ceremony, the crowd stood as two South Korean flags were raised and the South Korean national anthem played, the Associated Press reported...