Russia announced military exercises near the border with Ukraine on Monday in a show of strength as the Ukrainian army recaptured more territory from pro-Russian separatists in the east of the country.
The Russian air force said that more than 100 aircraft, including fighter jets and bombers, were taking part in the manoeuvres this week in the central and western military districts.
The move could alarm Western powers which have accused Russia of beefing up its troops along its border with Ukraine and arming the rebels in eastern Ukraine, although Moscow denies the accusations.
The manoeuvres include missile-firing practice and will assist “coordination between aviation and anti-missile defence”, Interfax news agency quoted an Airforce spokesman as saying.
He said Russia’s latest bomber, the Su-24, was taking part, as well as Su-27 and MiG-31 fighter jets.
Russia upset the West by staging military exercises near Ukraine in March after the conflict with Ukraine flared. Moscow said in May that it had pulled back its forces but NATO military commander General Philip Breedlove said last week it still had more than 12,000 troops and weapons along the frontier.
The crisis has pushed relations between Russia and the West to their lowest level since the Cold War, with each side accusing the other of orchestrating events in Ukraine, and the United States and European Union imposing sanctions on Russia.
Russia has a firm grip on the Crimea Peninsula, which it annexed in March after Ukraine ousted a pro-Moscow president, but the rebels who wanted Moscow to also annexe east Ukraine have been losing ground in the past few weeks.