Another US citizen has been detained in North Korea for suspected hostile acts against Pyongyang, authorities said on Sunday.

The man, named Kim Hak-song, was arrested on Saturday by “a relevant institution of North Korea” on suspicion of hostile acts, Xinhua news agency cited the official Korean Central News Agency.

It was the second time within one month that North Korea has arrested American citizens for allegedly carrying out hostile activities against Pyongyang.

The report said Kim “had worked for operation of Pyongyang University of Science and Technology”.

“A relevant institution is now conducting detailed investigation into his crimes,” said the report without citing any source.

North Korea arrested a US citizen for alleged hostile activities in April at Pyongyang airport.

Both arrested are of Korean origin and had worked here as teachers.

There are two other US citizens serving jail sentences for anti-North Korea activities.

North Korea said on Friday it has foiled a plot by spy agencies of the United States and South Korea to assassinate its top leader Kim Jong-un during mass celebrations last month. An unspecified number of suspects have been arrested in the case.

It is not known whether the latest two arrests of US citizens were connected with the case.