North Korea has called a February raid on its embassy in Spain by a shadowy anti-regime group “a grave terrorist attack,” state-run media said Sunday in Pyongyang’s first reaction to the break-in.

A spokesperson for the North’s Foreign Ministry labeled the raid “an illegal intrusion into and occupation of a diplomatic mission and act of extortion,” the official Korean Central News Agency (KCNA) reported, with the spokesman calling it “a grave breach of state sovereignty and a flagrant violation of international law.”

The raid saw a group of reportedly armed men break into the Madrid embassy compound, allegedly roughing up employees and stealing computers and key documents.

Free Joseon, a mysterious dissident group, claimed responsibility for the break-in but denied that anyone was “gagged or beaten” and said that “no weapons were used.” The group said Wednesday its actions were in response “to an urgent situation in the Madrid embassy” and that it had “shared certain information of enormous potential value” it obtained from the embassy with the FBI at its request.

The KCNA report quoted the Foreign Ministry spokesman said Pyongyang is “following the rumors of all hues now in the air” that the FBI “and the small fry” anti-North Korean group were involved in the “terror incident.”

It said the North expects Spanish authorities to “carry out an investigation into the incident to the last in a responsible manner in order to bring the terrorists and their wire-pullers to justice in conformity with the relevant international law.”

“This kind of act should never be tolerated,” it added.

The United States has denied it had anything to do with the raid, which came just days ahead of a second nuclear summit between North Korean leader Kim Jong Un and U.S. President Donald Trump in Hanoi. That meeting ultimately collapsed after the two sides failed to reach an accord.

An investigation into the raid is already underway 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.” A day later, the group released a short statement saying that its activities had been suspended after “speculative” articles in the media and that the media should refrain from focusing on individual members of the group.

Previously known as the Cheollima Civil Defense, the group — which offers assistance to people attempting to defect from North Korea — first emerged in 2017, claiming to be providing protection for Kim Han Sol, the son of Kim Jong Nam, the half brother of Kim Jong Un who was assassinated, allegedly by agents from his brother’s regime, at Kuala Lumpur International Airport in Malaysia in February 2017.

In March, the group declared itself to be North Korea’s government-in-exile, calling itself Free Joseon. Joseon is an old name used to refer to the Korean Peninsula.