WASHINGTON (AP) — A U.S. military official says a Russian fighter jet made multiple, close-range passes near an American warship in the Black Sea for more than 90 minutes Saturday amid escalating tensions in the region.

The official says the fighter flew within 1,000 yards of the USS Donald Cook, a Navy destroyer, at about 500 feet above sea level, saying this prompted ship commanders to issue several radio warnings. The fighter appeared to be unarmed and the passes ended without incident.

The USS Donald Cook was operating in international waters east of Romania. It was deployed to the Black Sea April 10th, in the wake of the Russian military takeover of Ukraine’s Crimea region and ongoing unrest there. The official was not authorized to talk publicly and spoke on condition of anonymity.