MADRID (Reuters) - A Spanish judge plans to request the extradition from the United States of members of a group he suspects of forcing their way into the North Korean embassy in Madrid and trying to persuade an official there to defect, a judicial source said on Tuesday.

The judge believes a group of 10 intruders identified themselves during the assault as human rights campaigners, according to a Spanish High Court document.

The group’s leader contacted the U.S. Federal Bureau of Investigation (FBI) a few days later to pass on information about the raid, the document said.

A judicial source told Reuters the judge believes all the identified suspects went to the United States after the raid and that he would request their extradition to Spain, where they could face up to 28 years in prison.

State Department spokesman Robert Palladino said the U.S. government was not involved in the raid, which Spanish High Court documents said involved a Mexican citizen who is a U.S. resident and a U.S. citizen, as well as South Korean citizens.

“The United States government had nothing to do with this,” Palladino told a regular news briefing, stressing that the United States called for the protection of all embassies.

He referred questions about the investigation to Spanish authorities. The State Department did not respond immediately to a request for comment about the extradition request.

The FBI said in a statement it was “our standard practice to neither confirm nor deny the existence of an investigation”, adding that the agency had a strong working relationship with Spanish law enforcement partners.

Spain’s Interior Ministry had previously said police were investigating an incident at the embassy on Feb. 22 but gave no details, except to say that a North Korean citizen had been injured and that no one had filed a complaint.

A Mexican citizen who is a U.S. resident, identified as Adrian Hong Chang, led the group, the Spanish High Court said in the document, based on the investigation of the incident.

The Adrian Hong Chang named by the court is a longtime activist who helped co-found the refugee aid organization Liberty in North Korea (LINK), and later led an organization preparing for an “imminent, dramatic change” in North Korea, according to NK News, a website that monitors North Korea.

He has usually gone by Adrian Hong in his professional affiliations and in op-eds about North Korea penned for numerous American publications.

LINK said Hong was a co-founder as a college student but had not been involved with the organization for more that 10 years.

The court identified the U.S. citizen as Sam Ryu.

The group stole computers, hard disks and pen drives, it said. It was not clear how the court knew that Hong had contacted the FBI.

Three of the intruders took an embassy official into the basement and encouraged him to defect from North Korea. They identified themselves as members of a group which campaigned for the “liberation of North Korea”, the document said.

A dissident organization called Cheollima Civil Defense acknowledged on its website late on Tuesday that it was behind the incident but said it was not an attack and that the group had been invited into the embassy.

Cheollima, also known as Free Joseon, said no one was gagged or beaten and that no governments were involved.

It said identifying individuals involved would “aid and abet the regime in Pyongyang”. It did not acknowledge any of the names in the court documents.

FAKE GUNS, BALACLAVA MASKS

The Washington Post reported earlier this month that Cheollima Civil Defense had carried out the raid. The paper quoted unidentified sources as saying last week that the group shared information about the raid with the FBI.

FILE PHOTO: A Spanish National Police car is seen outside the North Korea's embassy in Madrid, Spain February 28, 2019. REUTERS/Sergio Perez/File Photo

A source familiar with official U.S. government reporting on the incident said that, while they were not 100 percent positive, U.S. government experts found it plausible that Cheollima Civil Defense carried out the raid. The source did not want to be otherwise identified.

The Spanish court document gave a detailed account of the intruders’ movements before as well as during the intrusion, including their stay in a hotel and purchases of knives, balaclava masks and fake guns.

There was no immediate comment on the matter from South Korea’s Foreign Ministry. Spain’s Interior Ministry and Mexico’s foreign ministry declined to comment.

The embassy raid occurred shortly before the Feb. 27-28 summit in Hanoi between North Korean leader Kim Jong Un and U.S. President Donald Trump.

The Mexican, Hong Chang, said he carried out the raid voluntarily and did not identify his companions, the court document said.

Sung-Yoon Lee, a North Korea expert at Tufts University in the United States, said he was shocked that the names should have been revealed in the Spanish documents. He said this could put the lives of members of the group - including a U.S. citizen, a U.S. resident and citizens of a close ally, South Korea - at risk from North Korean reprisals.

“It seemed clear to me that the FBI had initially taken the position that the intel assets the group had retrieved at the embassy warranted the protection of the identities of the group,” he said.

“That the Spanish government has not redacted the names of the persons implicated is also quite shocking,” he said.

“Observing this extraordinary situation unfold, who in the future would collaborate with the United States government were they ever to come into possession of high-value intelligence on North Korea obtained illegally?” Lee said.

The FBI declined to comment when asked about the risk of North Korean reprisals.

According to the court document, the group kept embassy staff tied up for several hours and then searched the premises for arms before leaving, at which point they separated into four groups and headed to Portugal.

Hong Chang then flew from Lisbon to New York.

In Spain, the High Court has the power to investigate criminal offences, after which formal accusations are launched.