North Korea has detained another American Christian on suspicion of 'hostile acts' as tensions ramp up between the two states.

Kim Hak-song worked at Pyongyang University of Science and Technology (PUST) and previously described himself as a Christian missionary, according to Reuters.

He went to the volatile state, considered the worst place in the world for persecuting Christians by Open Doors, to start an experimental farm at the university in order to help the people become self-sufficient.

He was detained on Saturday and 'a relevant institution' was 'conducting a detailed investigation' into Kim Hak-song's alleged crimes, North Korea's state run news agency KCNA reported. No further details about his arrest or condition was given.

PUST was founded by an evangelical Christian entrepreneur in 2010 and mainly teaches North Korea's elite. Many of the teachers are foreign.

Washington said it was 'aware of reports that a US citizen was detained in North Korea' and would liaise with Pyongyang.

It comes in a series of high-profile detentions and if confirmed Kim Hak-song would the fourth US citizen currently held by the pariah state.

Kim Sang Dok, another US citizen teaching at the same Christian university, was detained in April according to state media.

The other two Americans already held in North Korea are Otto Warmbier, a 22-year-old student, and Kim Dong Chul, a 62-year-old Korean-American missionary.

Warmbier was detained in January 2016 and sentenced to 15 years hard labour for attempting to steal a propaganda banner.

Two months later, Kim Dong Chul was sentenced to 10 years hard labor for subversion. Neither has appeared in public since being sentenced.

The reported detention comes as tensions on the Korean peninsula run high, driven by harsh rhetoric from Pyongyang and Washington over the North's pursuit of nuclear weapons in response to what it says is a threat of US-instigated war.