The US military has said that Russian warplanes flew a "simulated attack" near American warship the USS Donald Cook in the Baltic Sea. The Russian Air Force allegedly flew a number of "unsafe and unprofessional" flights near the guided missile destroyer with one Russian Sukhoi Su-24 coming within 30ft (nine metres) of the ship.

According to unnamed officials it was so close the jets created "a wake in the water" near the vessel. The flights, by Su-24s and Ka-27 Helix anti-submarine helicopters, took place on 11 and 12 April in international waters off the coast of Poland, about 70 nautical miles off Kaliningrad.

US officials say that on 11 April, 20 passes were said to have been made at the USS Donald Cook by two Russian Su-24s coming within 1,000 yards at an altitude of just 100ft. The next day the "simulated attack profile" was said to have taken place – with aerial movements mimicking a real attack.

A Russian jet was said to have flown just 30ft (9 metres) above the warship during one operation. Two Russian Ka-27 Helix anti-submarine helicopters have also been accused of circling the ship seven times and taking photos.

According to Sky the incidents were described by US officials as "more aggressive than anything we've seen in some time" and at no point the Russian planes contacted the 20-year-old vessel's crew.

Russian actions were said to have been "unsafe and unprofessional" by the ship's commander and the US military believe the overflights have breached a 1973 treaty aimed at preventing incidents at sea. According to the US State Department this prohibits "simulating attacks".

In a statement, the US European Command said: "We have deep concerns about the unsafe and unprofessional Russian flight maneuvers. These actions have the potential to unnecessarily escalate tensions between countries, and could result in a miscalculation or accident that could cause serious injury or death."

Tensions between the US and Russia have been increased recently due to Russia's presence in Ukraine and their insistence in arming Bashar al-Assad's Syrian Army in the Middle East. The flyovers come as Nato plans its biggest Eastern European build-up since the Cold War.

On 31 March the US military announced that they will beef up its presence in eastern Europe as it plans to nullify an "aggressive" Russia. The plans include sending three armoured brigade combat teams based on a rotational basis in Estonia, Latvia, Lithuania, Poland, Romania, Bulgaria, and Hungary. The move follows a Pentagon announcement in February outlining plans to quadruple its budget for European defence in 2017.