Pyongyang marked a key military anniversary on Tuesday with a major artillery drill after Seoul announced joint naval exercises with a US aircraft carrier group this weekend.

Speculation has been mounting that Pyongyang would carry out a sixth nuclear test or another missile launch on Tuesday to mark 85 years since the founding of its army.

The Republic of Korea's Yonhap News Agency cited an unnamed government source as saying the Democratic People's Republic of Korea marked the anniversary with its "largest ever live artillery drill", carried out in the eastern port city of Wonsan and presumed to have been overseen by leader Kim Jong-un.