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 (March 26).

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

A few days later their leader contacted the US Federal Bureau of Investigation (FBI) to pass on information about the raid, the document said.

The 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 US government was not involved in the raid, which Spanish High Court documents said involved a Mexican citizen who is a US resident and a US citizen.

"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 embassies, whichever country they belonged to.

He referred questions about the investigation to Spanish authorities.

The FBI said in a statement it is "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 US 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 group stole computers, hard disks and pen drives, it said. It was not clear how the court knew that the man 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 who campaigned for the "liberation of North Korea", the document said.

The Washington Post reported earlier this month that a dissident organisation called Cheollima Civil Defence had carried out the raid.

The paper last week quoted unnamed sources as saying that the group shared information about the raid with the FBI.

FAKE GUNS, BALACLAVA MASKS

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.

The group included a US citizen and South Korean citizens.

There was no immediate comment on the matter from South Korea's Foreign Ministry. Spain's Interior Ministry declined to comment.

The embassy raid occurred shortly before the Feb 27-28 summit between North Korean leader Kim Jong Un and US.

President Donald Trump in Hanoi.

The Mexican, Hong Chang, said he had carried out the raid voluntarily and he did not identify his companions, the court document said. The court identified the US citizen as Sam Ryu.

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.