Moscow (Reuters): Russian nuclear-capable strategic bombers have flown over the Pacific Ocean, the Sea of Japan , the Yellow Sea and the East China Sea, prompting Japan and South Korea to scramble jets to escort them, Russia said on Thursday.

Russia 's Defence Ministry said in a statement the Tupolev-95MS bombers , code named "Bears" by NATO, flew over neutral waters and were accompanied by Russian Sukhoi-35S fighter jets and A-50 early warning and control aircraft.

It gave no details about the overall number of aircraft that had taken part in what it called a pre-arranged flight and did not say when or why the mission took place.

The TU-95MS bombers were refueled in mid-air during the mission , the ministry said.

During parts of the route, the bombers were escorted by South Korean and Japanese military jets, it added.

Russia , which shares a border with North Korea, has repeatedly voiced concerns about rising tensions on the Korean Peninsula caused by Pyongyang's nuclear missile program, and has complained about Japan 's plans to deploy a U.S. anti-missile system on its soil.