Russian Defense Minister Sergei Shoigu and U.S. Defense Secretary Lloyd Austin held a phone conversation on Wednesday to exchange views on the causes and consequences of a U.S. drone crashing into the Black Sea on Tuesday.

Shoigu pointed out that the causes of the incident were the U.S. non-compliance with the declared flight restriction zone set by Russia in connection with its special military operation as well as the strengthened U.S. intelligence activities against Russia, the Russian Defense Ministry said in a statement.

Shoigu noted that the flights of American strategic drones off the coast of Crimea are of a provocative nature, which creates prerequisites for an escalation of the situation in the Black Sea region.

Austin declined to offer any details of the call, but he reiterated at a news conference that the U.S. intended to continue flying where international law allowed and demanded Russian military aircraft operate in a safe and professional manner.

The statement from Russia's defense ministry said Russia is not interested in such a development of events but it will continue to respond proportionately to all provocations, adding that the two countries should "act with a maximum of responsibility" including by having military lines of communication in a crisis.

The U.S. military has said two Russian Su-27 fighter planes approached its MQ-9 Reaper drone on a reconnaissance mission over the Black Sea's international waters on Tuesday. The fighters harassed the drone and sprayed fuel on it before one clipped the drone's propeller, causing it to crash into the sea.

However, the Russian side said there was no collision. The drone crashed after making "sharp manoeuvres," having "deliberately and provocatively" flown close to Russian air space. Moscow had scrambled its fighters to identify it.

At present, Moscow has said it intends to recover the wreckage of the U.S. drone, while the U.S. officials said the debris is in such deep water that the recovery is impossible and would have no real intelligence value.

"I don't know whether we'll be able to retrieve it or not but it has to be done. And we will certainly work on it," Russian Security Council secretary Nikolai Patrushev said in televised remarks.

Senior Washington official John Kirby said in an interview with ABC News that the U.S. is also working to recover the drone from the Black Sea, admitting that it will be a challenging task.

But Kirby added that "we're comfortable that should anything be taken by the Russians, their ability to exploit useful intelligence will be highly minimized."

(With input from agencies)

(Cover: A U.S. MQ-9 drone is on display during an air show at Kandahar Airfield, Afghanistan, January 23, 2018. /CFP)