Seoul (AFP) - North Korea fired off an "unidentified projectile" Sunday according to South Korean defence officials, a week after its latest missile launch.

"North Korea fired an unidentified projectile at Pukchang, South Pyongan province in the afternoon today," the South's Joint Chiefs of Staff said in a statement.

There was no further information given about the nature of the projectile.

Last week Pyongyang launched an intermediate-range missile named the Hwasong-12 its longest-range missile yet, according to analysts.

It was its 10th launch this year, after dozens in 2016, as it accelerates efforts to develop an intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead to the continental United States -- something President Donald Trump has vowed "won't happen".

Pyongyang has long had missiles that can reach targets across the South and Japan.