The US military has released photographs showing Russian SU-24 fighter jets "buzzing" close to an American warship sailing in the Black Sea on 10 February after the Russian defence ministry denied reports of the alleged incident.

Lt Col David Faggard, spokesman for the US military's European Command, said at least four Russian warplanes flew past the USS Porter at unusually low altitudes and at high speed, which the captain of the ship termed "unsafe and unprofessional".

The military spokesman said first an IL-38 propeller-engine maritime patrol aircraft flew past their warship in the Black Sea, followed by three Su-24 fighter jets. He added that the images show the Russian jets were flying very close to the deck of the USS Porter.

Faggard said the US guided missile destroyer was sailing in international waters at the time of the incident. The warship was returning after completing a joint military exercise with Romania – a fellow member of the North Atlantic Treaty Organization (Nato).

A Nato official told CNN incidents of Nato aircraft scrambling to intercept Russian warplanes approaching Nato airspace have gone up in the recent past. "Allied aircraft scrambled around 400 times to meet Russian aircraft over Europe in both 2014 and 2015. In 2016, allied aircraft scrambled around 800 times in response to Russian aircraft," the official said in a statement.

Meanwhile, the chairman of the US Joint Chiefs of Staff Gen, Joe Dunford, is in Baku, Azerbaijan, to meet his Russian counterpart Gen Valeriy Gerasimov to discuss deteriorating US-Russia military ties. The release of the images of the latest alleged Russian "fly-by" incident coincided with the meeting of the two defence leaders.

Marine Corps Lt Gen Frank McKenzie, the Joint Staff's director of strategic plans and policy, said in a Pentagon statement that the two defence chiefs did not discuss policy or political issues. The meeting was held to establish a link between the two men "so they see each other and have an opportunity to size each other up. It's very hard to do that over a telephone".

"Even at the height of the Cold War, we had a capability to talk to the Russians," McKenzie said, noting: "It doesn't reflect we agree with everything or even anything that they are doing; that's not the purpose of this discussion. The purpose is to establish and reinforce procedures for us to talk in case we have an incident where we need to exchange information rapidly."