Russia began conducting live missile tests in the Baltic Sea Wednesday, forcing the closure of Baltic commercial airspace and alarming Latvia, a member of NATO.

The tests, which come as tensions between the West and Russia are reaching a level unseen since the Cold War, were conducted in Latvia’s exclusive economic zone, an area just beyond Latvian territorial waters, Reuters reports.

“It is a demonstration of force,” Latvian prime minister Maris Kucinskis told Reuters. “It is hard to comprehend that it can happen so close to [our] country.”

The Russian Defense Ministry announced the live-fire drills Monday, casting them as a routine exercise in striking air and sea targets. But Latvian officials pointed out that the drills have never been conducted so close to their territory.

NATO secretary general Jens Stoltenberg told reporters in Ottawa that the weapons tests were being closely monitored and issued a reminder that all sovereign nations have the right to conduct military exercises.

“We are staying vigilant and we are also increasing the readiness of our forces, especially in the Baltic region,” he told reporters after meeting with Prime Minister Justin Trudeau.