Officials in the United States are scrambling to identify the source of an apparent breach of highly classified documents.

The leak reportedly gives details on a range of topics, including Ukraine's air defense and Israel's spy agency.

Chris Meagher, assistant to the secretary of defense for public affairs, told reporters on Monday that the online leaks presented a "very serious" risk to national security. 

What is the latest?

Defense Secretary Lloyd Austin has reached out to allies and worked to assess the leaks since he became aware of them on Thursday, Meagher said. The department is looking closely at "how this type of information is distributed and to whom," he added. 

State Department spokesman Vedant Patel told reporters that officials "are engaging with allies and partners at high levels over this, including to reassure them of our commitment to safeguarding intelligence and the fidelity of securing our partnerships."

While the Defense Department is still assessing the validity of photographed documents circulating online, they "appear to contain sensitive and highly classified material," Deputy Pentagon Press Secretary Sabrina Singh said on Sunday.

Twitter, Telegram, Discord and other platforms have seen a flow of leaked documents in the last few days and new documents continue to appear online. 

What impact could the leaks have?

The areas addressed in the documents include Russia's war in Ukraine, China, the Middle East, and Africa.

News agency Reuters reports that one of the documents, dated February 23 and bearing the mark "Secret," mentions how Ukraine's S-300 air defense systems would be depleted by May 2 at the current usage rate.

Officials have told the Washington Post that some documents appear to have been manipulated but some others were consistent with CIA World Intelligence Review reports that are shared at high levels within the White House, Pentagon, and State Department.

The US media said that the leak could prove valuable to Russia by shedding light on how deeply US intelligence has penetrated parts of the Russian military structure.

Russia ridicules accusations of responsibility

Kremlin spokesman Dmitry Peskov on Monday described the leaks as "interesting," downplaying accusations that Moscow could be behind it.

"The leaks are reasonably interesting," Peskov said. "Everyone is studying, analyzing and discussing them widely." 

Asked about allegations that Moscow was behind the leaks, Peskov said: "I cannot comment on this in any way. You and I know that there is in fact a tendency to always blame everything on Russia. It is, in general, a disease."

South Korea to demand US take 'appropriate' action: report

Reuters reported that another document talks about internal discussions among top South Korean officials about US pressure on Seoul to help supply weapons to Kyiv and its policy of not doing so.

On Monday, the office of South Korea's  President, Yoon Suk Yeol, said that fact checks on the leaked documents were a priority. 

Yoon's office said that it would urge the US to take "appropriate" steps after confirming details, Yonhap news agency said.

The presidential office also said that the possibility that the documents were fabricated or a product of third-party interference cannot be ruled out, news outlet YTN reported. 

dvv/rc,fb (AFP, Reuters)