North Korea on Thursday called US President Donald Trump a 'psychopath' as tensions soar following the death of American student Otto Warmbier, who was evacuated in a coma from North Korean detention last week.

Pyongyang's official Rodong Sinmun newspaper said the US president was in a 'tough situation' at home and claimed he was toying with the idea of a preemptive strike on North Korea to divert attention from a domestic political crisis.

'South Korea must realise that following psychopath Trump... will only lead to disaster,' an editorial carried by the paper said.

North Korea on Thursday called US President Donald Trump a 'psychopath' as tensions soar following the death of American student Otto Warmbier

A series of atomic tests and missile launches since last year have ratcheted up tensions on the Korean peninsula, and Warmbier's death has further strained relations between Pyongyang and Washington.

Trump slammed the 'brutal regime' in Pyongyang, and said he was determined to 'prevent such tragedies from befalling innocent people at the hands of regimes that do not respect the rule of law or basic human decency.'

His language was echoed by South Korean President Moon Jae-In, who said in an interview ahead of a White House visit next week that North Korea bears responsibility for the student's death.

'I believe we must now have the perception that North Korea is an irrational regime,' Moon told CBS television's 'This Morning.'

Pyongyang's official Rodong Sinmun newspaper said the US president was in a 'tough situation' at home

Moon, a centre-left politician who was sworn in last month after a landslide election win, favours engagement with the North, rather than the hardline stance taken by his ousted conservative predecessor Park Geun-Hye.

Washington has also stepped up its muscle-flexing in the region, flying two B-1 bombers over the Korean peninsula Tuesday in a planned training mission with Japan and South Korea as its latest show of force.

Earlier this week, Otto Warmbier died six days after being brought back to the United States in a coma from North Korea.

The 22-year-old was returned to his family in Cincinnati, Ohio, on June 13 after spending 17 months in North Korea where he was arrested as a student for stealing a propaganda poster in January 2016.

Earlier this week, Otto Warmbier (pictured in March 2016) died six days after being brought back to the United States in a coma from North Korea

He returned in a vegetative state, unable to communicate with his family and with devastating brain loss. North Korean authorities dubiously blamed his condition on a bout of food poisoning which they said he suffered while imprisoned and released him on 'humanitarian grounds'.

On Monday, his family announced his death, laying the blame for it squarely with Kim Jong Un and his regime.

'The awful torturous mistreatment our son received at the hands of North Koreans ensured that no other outcome was possible beyond the sad one we experienced today,' Fred and Cindy Warmbier said in a statement.

President Trump shared his condolences with the family immediately, describing their son as 'North Korea's latest victim'.