Russia and ex-Soviet ally Belarus on Friday launched the active phase of vast military exercises involving 200,000 personnel that have alarmed Ukraine and some NATO nations.

The "Zapad-2021" war games, taking place on Russia's and Belarus's western flanks, are due to run until next Thursday. Moscow released footage of warships and tanks opening fire and fighter jets taking off.

The manoeuvres, the culmination of a three-month exercise, are held every four years.

At talks with his Belarusian counterpart on Thursday, President Vladimir Putin denied the exercises were directed against any foreign power, but said they were entirely logical given what he said was increasing NATO activity near Russia's borders and those of its allies.

The Western NATO alliance, whose officials have said Russia has regularly underreported the size of the exercises in the past, has urged Russia to be transparent and said it will be watching closely.

Russia sees Belarus as a strategically important buffer to its west, and helped to keep President Alexander Lukashenko in power with loans and political backing as he cracked down on huge protests last year and arrested or drove out opposition figures.

Putin and Lukashenko are due to inspect the exercises personally, according to Belarusian state media, though it was not clear when that would happen.

Russia's Defence Ministry said the active phase of the drills would take place at nine sites in Russia and five sites in Belarus. The exercises involve 200,000 personnel, 80 planes and helicopters, 290 tanks and 15 naval ships, it says.

Military personnel from Armenia, India, Kazakhstan, Kyrgyzstan and Mongolia are also due to participate.

(Reporting by Tom Balmforth; Editing by Kevin Liffey)