North Korea's state media gave the South's President Moon Jae-in a "fail" grade on Friday for his first 100 days in office, dismissing his proffered olive branches as "hypocrisy".

Moon, elected to replace impeached President Park Geun-hye, came into office in May and has since had to deal with tensions over North Korea's missile and nuclear programmes.

Pyongyang carried out its first successful tests of an intercontinental ballistic missile (ICBM) last month, apparently bringing much of the US mainland within its reach.

At a briefing Thursday to mark his 100th day in office, Moon insisted there will be no second Korean war but urged the North to stop further nuclear and missile tests, warning Pyongyang to end its "dangerous gamble".

The Rodong Sinmun, the official mouthpiece of the ruling Workers' Party, responded on Friday with a withering commentary, saying the performance of Moon's 100 days was "poor and very disappointing".

It did not name Moon, describing him only as the "current power holder".

Relations between the two were "an absolute fail", it added, saying while Moon spoke of dialogue and implementing North-South agreements his actions moved in the opposite direction.

"The South authorities' utterances about improving intra-Korean ties turned out to be nothing but hypocrisy," it said.

"The South's power holder says he is pushing for sanctions and pressure while seeking to open dialogue at the same time. This is an unpardonable plot toeing the US line to suffocate the DPRK," it said, using the abbreviation of the North's official name.

"Dialogue and sanctions simply cannot go together," it asserted.

Moon is enjoying strong ratings in South Korea.

READ MORE: North Korea's nuclear weapons: Here's what we know

North Korea's ICBM tests sparked weeks of sabre-rattling with Washington, with Pyongyang threatening to fire a salvo of rockets towards the US territory of Guam. US President Donald Trump has warned of "fire and fury" and said Washington's weapons were "locked and loaded".

Tensions have since eased with North Korea's leader Kim Jong-un saying he would watch the "Yankees" for a time before deciding whether to proceed with the Guam plan.

But the atmosphere is likely to worsen again next week when the United States and South Korea kick off their annual Ulchi Freedom Guardian military drills.

Pyongyang views the exercises as a highly provocative rehearsal for an invasion of its territory and regularly carries out counter-actions of its own, such as missile launches.