Putin told reporters that 14 strategic bombers, along with support and refuelling aircraft, had taken off from seven airfields across the country at midnight.

"We have decided to restore flights by Russian strategic aviation on a permanent basis," he said after meeting Hu Jintao, China's president, at a joint military exercise with China and four Central Asian states in Russia's Ural mountains.

"Patrolling will take place in areas of busy shipping and economic activities of the Russian Federation."

'Different era'

Sean McCormack, US state department spokesman, said: "That is a decision for them to take."

"It's interesting. We certainly are not in the kind of posture we were with what used to be the Soviet Union. It's a different era.

"If Russia feels as though they want to take some of these old aircraft out of mothballs and get them flying again, that's their decision."

Sean McCormack, US state department spokesman
"If Russia feels as though they want to take some of these old aircraft out of mothballs and get them flying again, that's their decision."

Soviet bombers capable of carrying strategic nuclear weapons routinely flew missions to areas from which they could be launched at the United States during the Cold War.

Earlier, Colonel Alexander Drobyshevski, a spokesman for the Russian air force, was quoted by the Itar-Tass news agency as saying: "At present, there are several pairs of Tu-160 and Tu-95MC planes over the waters of the Atlantic and Pacific oceans, being escorted by Nato aircraft.

"During the course of the day around 50 flights will be carried out."

Earlier this month Russian air force generals said bomber crews had flown near the Pacific island of Guam, where the US military has a base, and "exchanged smiles" with US pilots who had reportedly scrambled to track them.

The Pentagon said the Russian aircraft had not come close enough to US ships to prompt a reaction.

Tense relations

Relations between Moscow and Washington are currently strained. The US has criticised Russia's democratic record while Moscow is angered by US plans to base a missile defence system in eastern Europe.

"This is a significant change of posture of Russian strategic forces," Alexander Pikayev, a senior military analyst with the Moscow-based Institute for World Economy and International Relations, said.

Russia, China and four Central Asian nations
took part in joint exercises [AFP]
 
"It's a response to the relocation of Nato forces closer to Russia's western border."

Six thousand troops took part in the war games which came at the close of the annual summit of the Shanghai Co-operation Organisation.

Washington will have been watching with interest as the group is increasingly being seen as an eastern power block aimed at curbing US dominance in world affairs.

A communique issued at the end of the summit included what was seen as a thinly-veiled warning to the US to stay out of the region.

"Stability and security in Central Asia are best ensured primarily through efforts taken by the nations of the region on the basis of the existing regional associations,'' the statement said.