NATO say there is no sign or indication that Russia is preparing military action against the alliance.
A rocket landed in Poland last night and killed two people on rural farmland.
Polish media said missiles hit an area where grain was drying in Przewodow, a village in eastern Poland near the border with Ukraine.
Moscow launched a large number of missiles at Ukraine on Tuesday, knocking out power for seven million households.
Initially, there were fears that it was a Russian rocket attack which hit the area of Poland close to Ukraine.
However, NATO believe the rocket was from Ukrainian air defences.
An emergency meeting of NATO took place today.
Secretary General Jens Stoltenberg said "an investigation into this incident is ongoing.
"We need to await its outcome, but we have no indication this was the result of a deliberate attack.
"And we have no indication that Russia is preparing military action against NATO."