North Korean leader Kim Jong Un has inspected artillery drills by units that are said to be in firing range of the South Korean capital, Seoul.

North Korea's ruling Workers' Party newspaper, Rodong Sinmun, said on Friday that the exercises that took place the previous day were aimed at strengthening combat mobilization readiness and actual war capability.

Photos show launchers lined up on a beach and firing in unison.

The article said the drills involved long-range artillery units that are in firing range of "the enemy's capital."

Observers say they may have been conducted to prepare for a surprise attack on Seoul.

Kim reportedly called for strengthening all the artillery sub-units so they can take the initiative with rapid strikes "at the moment of their entry into an actual war."

The North Korean leader inspected military units training for war on Wednesday.

His intention is to apparently counter the US and South Korea. The two countries began joint military drills on Monday to prepare for a contingency on the Korean Peninsula.