WASHINGTON : An armed Russian fighter jet intercepted a US military reconnaissance plane in late April in international airspace over the Sea of Okhotsk, several days after another intimidating maneuver in the Black Sea, the Pentagon disclosed Tuesday.

US Defense Secretary Chuck Hagel and the Chairman of the Joint Chiefs of Staff General Martin Dempsey both communicated US concerns over the incident directly to the Russians, Pentagon spokesman Colonel Steven Warren said. Warren said the US RC-135 reconnaissance plane was on a routine mission over international airspace when it was intercepted by an Su-27 fighter.

‘The Su-27 approached the RC-135 across the nose of the US aircraft at approximately 100 feet,’ he said. The US aircraft’s crew members were able to see that the Russian plane was armed when it briefly exposed its belly during the maneuver, he said. The incident occurred over the Sea of Okhotsk, which lies in the Pacific north of Japan between Sakhalin Island and the Kamchatka Peninsula in Russia’s east.

The incident comes amid heightened tension between Washington and Moscow over the crisis in Ukraine. Less than two weeks earlier, on April 12, a Russian Su-24 fighter bomber made a low pass over the destroyer USS Donald Cook as it cruised in international waters in the Black Sea. At the time, the Pentagon denounced the incident as ‘provocative and unprofessional.’ Warren said he was not aware of any other incidents involving Russian aircraft since April 23. ‘We continue to conduct normal operations,’ he said.