Leader Kim Jong Un has joined North Korean soldiers training in operating a new battle tank, according to state media, as rivals South Korea and the United States wrapped up joint military exercises.

Sporting a black leather jacket, Kim watched live-fire “training march” exercises from a field command post before mounting the new tank and driving it himself, the official Korean Central News Agency (KCNA) reported on Thursday.

Kim expressed “great satisfaction” that the tank – first unveiled during a 2020 military parade – demonstrated its striking power in its inaugural performance display and told his troops to bolster their “fighting spirits” and complete “preparations for war”, KCNA said.

This was the third time Kim, who last week had also ordered heightened readiness for war, was reported to have observed military exercises in the past month. The other two drills he inspected were dedicated to artillery firing and manoeuvring exercises.

North Korea’s Ministry of Defence last week threatened “responsible military activities” in reaction to the South Korea-US training, which the North views as rehearsals for an invasion.

The US and South Korea have been expanding their training exercises, with the latest round involving a computer-simulated command post training and 48 kinds of field exercises.

North Korea’s military preparations follow a speech by Kim in January in which he pledged to rewrite the constitution to eliminate the country’s longstanding goal to seek peaceful unification of the Korean Peninsula and cement South Korea as its “invariable principal enemy”.

He said the new constitution must specify North Korea would annex and subjugate the South if another war broke out.