In March North Korea launched several missiles that landed in the Sea of Japan. The move prompted the US to deploy a missile defence system to South Korea.
In early April North Korea attempted to launch another missile towards Japan, however this one exploded after about 60km, also landing in the Sea of Japan, according to South Korea's defence ministry.
In late April North Korea's foreign ministry issued a statement warning Australia over its allegiance to the US.
"If Australia persists in following the United States' moves to isolate and stifle [North Korea] and remains a shock brigade of the US master, this will be a suicidal act of coming within range of the nuclear strike of the strategic force of [North Korea]," it read.
United States president Donald Trump, meanwhile, has labelled North Korean leader Kim Jong-un a "smart cookie" and said he would be honoured to meet with him.