Ukraine: How big is Russia's military build-up?

Russia has moved about 100,000 troops - equipped with everything from tanks and artillery to ammunition and air power - to Ukraine's border but denies it is planning an invasion.

About 35,000 Russian personnel are permanently stationed near Ukrainian territory.

And on Wednesday, the Russian defence ministry released pictures of military units on their way to a training site in Rostov, close to Ukraine's border.

Some newly arrived units have travelled almost 4,000 miles, from the Russian Far East.

Most estimates put the number of Russian troops deployed around Ukraine - to the country's north, south and east - at about 100,000.

On Tuesday, UK Prime Minister Boris Johnson said: "The intelligence is very clear that there are 60 Russian battle groups on the borders of Ukraine," about a third of the total available numbers.

In addition to the regular Russian troops, there are thought to be about 15,000 Russian separatists in Ukraine's Luhansk and Donetsk regions.

But some Western analysts say it is not clear that Russia has assembled everything needed for a ground invasion.

They point to the absence of fully manned mobile field hospitals in some areas.

The arrival of medical staff, they say, could indicate readiness to attack.

Satellite images provide additional clues.

The presence of troops can sometimes be detected by the colour of tents.

Those occupied are heated, melting the snow on their roofs and appearing darker from above.

Armoured vehicles can be identified by their shapes.

And tyre tracks or mud indicate vehicles on the move.

A Russian force of several thousand has been moved to Belarus for a joint military exercise that will reach its peak between 10 and 20 February.

The country's leader, Alexander Lukashenko, supports Russian President Vladimir Putin.

The Ukrainian capital, Kyiv, is less than 100 miles (150km) from the Belarus border.

And Western observers say the exercise, Allied Resolve, could provide an opportunity to rehearse a mission against Ukraine.

Images posted online claim to show military equipment, including armoured vehicles, tanks and rocket systems, travelling towards the area.

And Russia has announced the deployment of advanced Su-35 fighter planes to Belarus, along with air-defence systems, munitions and medical support.

Russia is holding worldwide naval drills, from the Atlantic to the Pacific, starting this month and running through February, involving about:

Six Russian Navy vessels, capable of landing main battle tanks, personnel and armoured vehicles, have passed through the English Channel on their way to exercises in the Mediterranean Sea.

But it is unclear whether the Black Sea and the Ukrainian coast may be their intended destination.

Some analysts say an amphibious landing by Russian troops would be extremely difficult and the naval forces may be a "feint" to draw Ukrainian ground forces away from more likely routes of attack on land.

Graphics by Sandra Rodriguez Chillida and Prina Shah