U.S. Secretary of State John Kerry on Thursday condemned as dangerous and provocative a military encounter in the Baltic Sea, with Russian warplanes flying very close to a US military ship.

“We condemn this kind of behaviour. It is reckless. It is provocative. It is dangerous. And under the rules of engagement that could have been a shoot-down,” Mr. Kerry said in an interview with CNN Espanol and the Miami Herald.

“People need to understand that this is serious business and the United States is not going to be intimidated on the high seas. … We are communicating to the Russians how dangerous this is and our hope is that this will never be repeated.”

State Department spokesman John Kirby said Kerry will raise the incident with Russian Foreign Minister Sergei Lavrov, as Reuters report.