By Barry Neild, CNN

London, England (CNN) -- Rare photos of Russian strategic bomber jets purportedly intercepted in British airspace show Moscow's war machine is becoming increasingly bold, analysts said Thursday as Russia denied any territorial violations.

Britain's Ministry of Defence released images it said were taken earlier this month of two Russian Tu-160 bombers -- known as Blackjacks by NATO forces -- as they entered UK airspace near the Outer Hebrides islands off Scotland's northwest coast.

It said the March 10 incident, which resulted in crystal clear images of the planes against clear blue skies and a dramatic sunset, was one of many intercepts carried out by British Royal Air Force crews in just over 12 months.

"This is not an unusual incident, and many people may be surprised to know that our crews have successfully scrambled to intercept Russian aircraft on more than 20 occasions since the start of 2009," Wing Cdr. Mark Gorringe, of the RAF's 111 Squadron, said in a statement.

The RAF said two of its Tornado fighter jets from its base at Leuchars, on Scotland's east coast, were dispatched to tail the Russian Blackjacks as they approached the western Isle of Lewis.

"The Tornados shadowed the Russians as they flew south, then the Blackjacks turned north, just short of the Northern Ireland coast, and eventually left UK airspace," the statement said.

"After four hours, the Tornado crews stood down and returned to Leuchars."

Several of the images show the name Vasily Reshetnikov in Russian lettering near the cockpit of one plane. Reshetnikov was a celebrated Soviet pilot who fought on the Eastern Front in World War II.

Russian military authorities on Thursday confirmed their aircraft had been in the area, but denied any violation of British airspace.

"Our planes fly in strict accordance with the international rules government the use of airspace over neutral waters without violating the borders of foreign countries," Defense Ministry spokesman Lieutenant-Colonel Vladimir Drik told CNN.

"The routine flights by the Tu-160 missile carriers took place in accordance with those conditions on March 10. They did not violate British airspace, and objective control materials confirm that."

Experts say regardless of the exact flight paths, the increased sorties by Russian aircrafts in international airspace show Moscow is flexing its muscles as it re-emerges as a global military player.

"Russia is now an oil exporting state so they've got more money to spend on their armed forces after the 1990s when they were bankrupt," defense analyst Tim Ripley told CNN.

Ripley said the increase in air activity began shortly before Russia's brief 2008 territorial skirmish with Georgia, but while it was a clear show of strength, it did not represent sinister intent.

While ties between Russia and the UK have been strained in recent years, Ripley said talks with Washington that look set to result in a new arms control deal were a clearer indication of Moscow's global military outlook.