North Korea on Sunday described the February raid on its embassy in Madrid by a dissident group as a “grave terrorist attack” and urged an investigation into the perpetrators.

A group of armed men burst into Pyongyang’s Spanish embassy last month and roughed up employees before fleeing with documents and computers.

The incident came just days before a high-stakes nuclear summit in Hanoi between the North Korean leader, Kim Jong-un, and Donald Trump that ultimately failed to reach an accord.

In its first official comment on the raid, North Korea suggested Washington’s possible involvement and called on Spanish authorities to bring the “terrorists and their wire-pullers to justice”.

“A grave terrorist attack occurred on February 22, where an armed group assaulted the DPRK embassy in Spain,” a spokesman for the foreign ministry said in a statement carried by the official KCNA news agency, using the acronym for the North’s official name.

“We expect that the authorities concerned in Spain ... carry out an investigation into the incident to the last in a responsible manner.”

An investigation into the raid is already under way in Madrid.

On Wednesday, a Spanish court named Mexican national Adrian Hong Chang as leader of the group who contacted “the FBI in New York five days after the assault” with information related to the incident in the embassy.

Hours after the court statement, the Cheollima Civil Defense (also known as Free Joseon) – a dissident group believed to include high-profile North Korean defectors – claimed responsibility for the raid.

• This article was amended on 2 April 2019 to include the Cheollima Civil Defense’s alternative name, Free Joseon.