Kim Jong-un has attended the testing of an unspecified new "tactical weapon" in North Korea, according to state media, in what is the first such inspection by the leader in almost a year.

In the latest development which threatens to sour improving relations between North Korea and the international community, state media said Mr. Kim oversaw the successful testing of a "newly developed ultramodern tactical weapon".

It didn't appear to be a nuclear device or a long-range missiles targeting the US mainland, but the KCNA news agency gave few further details over the nature of the weapon, only referring to it as a "steel wall" around North Korea and saying it had been developed over a long time.

The agency reported Mr. Kim expressed "great satisfaction" over the "state-of-the-art" weapon, saying that it "builds impregnable defences of our country and strengthens the fighting power of our people's army".

Nonetheless, North Korea hasn't publicly tested weapons of any kind since the launch of the Hwasong-15 intercontinental missile on 29 November last year. The decision to resume testing now could influence the direction of stalling talks with the US and South Korea over denuclearization and the normalization of ties.

In recent days Pyongyang has expressed anger at US-led international sanctions and ongoing small-scale military drills between Washington and South Korea. 

Earlier this month, North Korea's Foreign Ministry warned it could bring back its policy of bolstering its nuclear arsenal if it doesn't receive sanctions relief.  

And this week, a team of US analysts said they had identified 13 hidden North Korean missile bases, at least some of which still showed signs of activity in recent months.

The only picture released by state media showed Mr. Kim standing on a beach surrounded by officials in military uniforms, but no weapons were visible.

International weapons experts said the officials around Kim included a leader of the artillery corps of the Korean People's Army.

In Washington, in response to the North Korean announcement, a US State Department spokesman told the Reuters news agency: "We remain confident that the promises made by President Trump and Chairman Kim will be fulfilled." 

The official was referring to an unprecedented summit of between Mr. Kim and Donald Trump in Singapore in June, where they agreed to establish new relations with each other and work towards peace.

But the agreement was short on specifics, and negotiations have made little headway since.