North Korea fired at least one ballistic missile into waters off its east coast Wednesday, South Korea's Joint Chiefs of Staff said, as a highly anticipated meeting between Kim Jong Un and his Russian counterpart Vladimir Putin was set to take place in Russia's Far East.

The North Korean leader arrived in Russia on Tuesday, state media reported, aboard his heavily-armored private train accompanied by party leaders, including a top military official in charge of the country's ballistic missile programs, according to photos shared by North Korean state media KCNA.

This is a developing story. More to come.