NATO Secretary-General Jens Stoltenberg says allies have raised concerns about what they call Russia’s use of a kind of electronic warfare during military exercises last month that jammed some phone networks.

Stoltenberg said Thursday after a meeting between NATO and Russia ambassadors that “at least two allies have reported about that.”

He said it highlights the need for Russia to be more transparent with war games “to make sure there are no miscalculations, misunderstandings, because these kind of activities can have serious effects.”

Phone services in Latvia, Norway and Sweden’s Oeland islands were reported to have been shut down for a few hours during the Sept. 14-20 Zapad exercises Russia held with Belarus.

The jamming is suspected to have been done by a Russian communications ship in the Baltic Sea.

(AP)