(CNN)A Russian military jet violated NATO airspace on Friday while it was attempting to intercept a US Air Force B-52 bomber flying near the Danish island of Bornholm, the alliance said in a statement Monday, calling the incident a "significant violation of international law."

"The Russian Su-27, flying from Kaliningrad, followed the B-52 well into Danish airspace over the island, committing a significant violation of airspace of a NATO nation," NATO's Allied Air Command said in a statement.

"Danish Quick Reaction Alert aircraft were launched to counter the violation, however the violating Russian fighters turned back before interception," the statement added, saying, "The unauthorized intrusion of sovereign airspace is a significant violation of international law."

Kaliningrad is a Russian exclave between Poland and Lithuania that features a significant Russian military presence. Bornholm island sits in the Baltic Sea less than 90 miles east of Copenhagen.