A general view of North Korea's embassy in Madrid, Spain. The 10 people who allegedly raided the North Korean Embassy in Madrid last month belong to a mysterious dissident organization that styles itself as a government-in-exile dedicated to toppling the ruling Kim family dynasty in North Korea. File photo: AP Photo/Bernat Armangue.

Seoul - North Korea has condemned an apparent break-in at its embassy in Madrid last month as a "grave terrorist attack" and said it is monitoring rumours about FBI involvement, making its first official comments on Sunday in response to the incident.

The break-in is said to have taken place days before US President Donald Trump met with North Korean leader Kim Jong in Hanoi, but details on it have been murky.

On Sunday a Foreign Ministry spokesperson told state-run North Korean news agency KCNA that "a grave terrorist attack occurred on February 22, where an armed group assaulted the DPRK Embassy in Spain and bound, beat and tortured the Embassy staff and extorted the communication apparatus."

The spokesperson said the ministry was "following the rumours of all hues now in the air that FBI of the United States and the small fry of anti-DPRK [Democratic People's Republic of Korea] 'body' were involved in the terror incident."

North Korea expected that Spanish authorities would investigate "in a responsible manner in order to bring the terrorists and their wire-pullers to justice in conformity with the relevant international law."

This week a group opposed to Kim's rule and which calls itself the Cheollima Civil Defense published a statement claiming responsibility for the break-in.

It said no information from the embassy "was shared with any parties with the expectation of any benefit or money in exchange" but that it had "shared certain information of enormous potential value with the FBI in the United States."

US State Department spokesman Robert Palladino on Wednesday denied that the US had anything to do with the incident.