WARSAW - A search has been under way for four US soldiers who went missing during a military exercise in Lithuania, according to a NATO spokesperson on Wednesday evening.

"We regret any confusion about remarks" concerning the four soldiers, the spokesperson said on social media platform X, noting that NATO Secretary General Mark Rutte was referring to emerging news reports and the fate of the missing "is still unknown."

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Earlier in the day, Rutte told reporters in Warsaw that "We do not yet know the details, but it is terrible news," and he appeared to confirm that the soldiers had died.

The Lithuanian Armed Forces reported that the soldiers, along with a tracked vehicle, went missing on Tuesday afternoon during a training exercise at the General Silvestras Zukauskas training area in Pabrade, eastern Lithuania.

According to a statement released by the US Army on Wednesday, the tracked vehicle the soldiers had been operating was found submerged in a swamp.

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Lithuanian Defence Minister Dovile Sakaliene visited the training site late on Wednesday, and said that no bodies had been found. An investigation has been launched into the soldiers' disappearance.