Story highlights North, South Korea exchange fire after North opens up on balloons with anti-aircraft guns

The balloons carried leaflets critical of the North, South Korean Defense Ministry says

The exchange comes amid continuing speculation over the fate of the North's missing leader

North Korea has also made some diplomatic overtures in recent days

North and South Korea exchanged fire Friday after gunners in the North targeted balloons carrying leaflets critical of the country's reclusive regime, the South Korean Defense Ministry said.

North Korean gunners fired anti-aircraft rounds at the balloons for 20 minutes, and some of the shots landed on South Korean soil, the ministry said. After a warning, South Korea responded with a 40 rounds from a heavy machine gun, the ministry said.

South Korean activists released the balloons filled with fliers critical of the North on Monday, the Defense Ministry said.

The exchange is the latest in a series of similar incidents between the two countries, the most recent of which came Tuesday, when patrol boats from North Korea and South Korea exchanged fire in the Yellow Sea, according to the South Korean Defense Ministry.

A North Korean official said last week that the country was ready to resume negotiations over the country's nuclear efforts with Russia, the United States, China, Japan and South Korea.

High-ranking Pyongyang officials also visited South Korea on Saturday, saying the North was willing to hold a new round of diplomatic talks between the two countries.

North Korea has also reached out to the European Union. Ri Tong Il, the North Korean deputy ambassador to the United Nations, said Tuesday that North Korea and the European Union would hold human rights talks at the end of the year.

Kim's disappearance from public view has also stoked discussion about who is leading the country and what's next.

He missed a ceremony Friday in honor of his late father and grandfather on the 69th anniversary of one of the most powerful institutions in North Korean life, the Workers' Party of North Korea.

Kim, 31, who first appeared as the North's top leader in 2010, has not been seen publicly since September 3, according to NK News.