MOSCOW, April 12. /TASS/. Moscow knew even without American leaked documents about NATO countries’ involvement in what was happening in Ukraine, Kremlin Spokesman Dmitry Peskov told reporters on Wednesday.

"Like everyone else, we don’t know to what extent we can trust these documents," the Kremlin spokesman pointed out. "However, long before these documents popped up, we had and still have information that many instructors from NATO countries, including the UK, as well as fighters, are taking part in combat operations," Peskov stressed.

The US media earlier said, citing the US administration officials, that the Pentagon and the US Justice Department were investigating a leak of documents concerning the US and NATO’s plans to train Ukrainian soldiers ahead of an offensive against Russia. Numerous documents on the schedules of arms supplies and the strength of forces were leaked to social networks, including Twitter and Telegram.

These documents also contained information on the presence of NATO fighters in Ukraine, as well as on the work of foreign instructors.