Washington (CNN) A shadowy North Korean dissident group claimed responsibility for last month's raid on Pyongyang's embassy in the Spanish capital, Madrid on Tuesday but disputed allegations that what occurred at the diplomatic compound was an "attack" involving armed intruders.

Cheollima Civil Defense, a secretive organization whose goal is to overthrow the Kim regime in North Korea , also denied that any other foreign governments were involved in the operation or that it was related to President Donald Trump and Kim Jong Un's summit in Hanoi, which occurred days later.

"This was not an attack. We responded to an urgent situation in the Madrid embassy. We were invited into the embassy, and contrary to reports, no one was gagged or beaten. Out of respect for the host nation of Spain, no weapons were used. All occupants in the embassy were treated with dignity and necessary caution. There were no other governments involved with or aware of our activity until after the event," a statement released by CCD said.

"We have evidence verifying our account. It is to protect those who seek our help, and those who take great risk to protect others, that we cannot share more about the event at this time. We continue to be engaged in extraordinarily sensitive work around the world," it added.

The statement was released hours after a Spanish judge said Tuesday that the FBI was contacted by one of the alleged intruders who carried out last month's mysterious raid on the North Korean embassy in Madrid and offered stolen data taken during the brazen attack.

Judge José de la Mata lifted a secret decree on the investigation into the February 22 attack, providing "an account of what happened before, during and after the assault," according to a document from Spain's High Court

The alleged incident, was carried out by 10 people who the judge says identified "themselves as members of an association or human rights movement for the liberation of North Korea." The court document does not specifically name CCD.

Five days after the attack, the FBI was contacted by the group's alleged leader, a US resident, "in order to provide information regarding the incident at the Embassy, ​​as well as the audiovisual material allegedly obtained" during the raid, the document says.

"In addition, he stated that, under his own will, he carried out the events together with a group of unidentified persons," it adds.

The judge also said he believes the identified intruders, which include American and South Korean citizens, traveled to the US after the attack.

State Department deputy spokesperson Robert Palladino said Tuesday that the US government "had nothing to do with" the attack at the embassy. He also noted that the US "would always call for the protection of embassies belonging to any diplomatic mission throughout the world."

The FBI declined to comment.

CCD maintains that they shared information with the FBI voluntarily, but at the bureau's request.

"No information about Madrid was shared with any parties with the expectation of any benefit or money in exchange. The organization shared certain information of enormous potential value with the FBI in the United States, under mutually agreed terms of confidentiality. This information was shared voluntarily and on their request, not our own. Those terms appear to have been broken," the statement said, referring to media reports implicating them in the break in.

Spanish authorities confirmed earlier this month that they were investigating a reported attack on the embassy but declined to provide details about an ongoing probe.

Spain's Interior Ministry previously said it does not comment on active investigations.

Previous accounts of the attack published by the Spanish newspaper El País said a group of individuals carrying fake firearms entered the compound where they interrogated and beat up people inside.

The alleged assailants then restrained staff members with rope and stole a variety of items before fleeing in luxury vehicles, according to Spanish media reports.

Similar details were revealed in the Spanish court document released Tuesday.

A source familiar with the incident previously told CNN that the Cheollima Civil Defense, a shadowy North Korean dissident group, is believed to be behind the attack, which occurred days before US President Donald Trump and North Korean leader Kim Jong Un held their second summit, in the Vietnamese capital of Hanoi.

Trump and Kim's meeting ended abruptly in part due to disagreement over when to remove UN sanctions in exchange for steps toward Pyongyang's denuclearization. But Trump and his aides said both sides left on good terms.

The Washington Post was first to report the involvement of the secretive group. They were also first to report that the FBI was contacted by the alleged intruders.

The Cheollima Civil Defense first gained international recognition after it reportedly came to the defense of Kim Han Sol, the son of Kim Jong Nam. Kim Jong Nam, the elder half-brother of North Korea's leader, was exposed to the deadly nerve agent VX in 2017 while entering an airport in Kuala Lumpur, killing him in minutes. US, South Korean and Malaysian authorities have pinned the attack on Pyongyang, but North Korea has adamantly denied any responsibility.

It's unclear why Kim Jong Nam was killed, but analysts said that if North Korea was behind the murder, perhaps Kim Jong Un saw his brother and his family as a possible threat to his leadership.

"The Cheollima Civil Defense established credibility by acting quickly and getting Kim Han Sol, the son of Kim Jong Nam, within days of his father's gruesome assassination," said Sung-Yoon Lee, a professor at Tufts University Fletcher School of Law and Diplomacy.