North Korea called on Spanish authorities to investigate a Feb. 22 raid on its embassy in Madrid, calling it a “grave terrorist attack,” according to Reuters.

During the February incident, a group of 10 people led by Mexican national Adrian Hong Chang allegedly stole computers and documents from the facility, claiming to represent the Cheollima Civil Defense, an activist group that claims to aid defectors from North Korea. The group reportedly gagged the embassy’s business envoy, So Yun Sok, when he turned down their offer to defect.

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Hong Chang then traveled to the United States and contacted the FBI, offering them the materials stolen during the raid, according to Spanish officials.

In its first official comment on the incident, North Korea’s Ministry of Foreign Affairs called for a probe and said it was aware of rumors that the FBI helped organize the raid, although it did not go so far as to blame the U.S. for the incident, according to Reuters.

“An illegal intrusion into and occupation of a diplomatic mission and act of theft are a grave breach of state sovereignty and a flagrant violation of international law, and this kind of act should never be tolerated over the globe,” North Korean officials said, according to the news service.

The incident comes amid efforts to improve ties between the U.S. and North Korea, particularly after a second meeting between President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE and Kim Jong Un ended without the two leaders reaching a deal. Last week, Gen. Robert Abrams, commander of U.S. Forces Korea, told the House Armed Services Committee that North Korea's activities are "inconsistent" with denuclearization.