New Delhi, Mar 2 (IANS): The mayor of Kiev has warned the residents that Russian forces are moving in on Ukraine's capital and has urged people to stay indoors and prepare to defend the city, BBC reported.

"The enemy is massing forces closer and closer," said mayor Vitaliy Klitschko, adding that there was now fighting on the capital's outskirts.

"We are preparing and will defend Kyiv (Kiev)! I call on all Kyivans not to lose their fortitude".

So far Kiev has resisted Russian incursion attempts.

An armoured Russian convoy stretching 40 miles is approaching from the city's north, and analysts believe it could be there to provide support for an invasion attempt from the west, BBC reported.

Military expert Dr Jack Watling says the timing and manner of the Russian attack on Kiev is critical.

"If the Russians commit to a major assault [in Kiev] and they haven't broken the back of the resistance, it will be very bloody and their troops might break," says Watling, a research fellow in land warfare and military Sciences at the Royal United Services Institute, BBC reported.

He says Russians will want to "whittle down" the resistance before they commit their forces.

Watling says there is evidence of low morale among Russian troops, citing lost and confused advance units - and their initial surprise at coming under fire from Ukrainians.

"We have heard reports of them damaging their own equipment because they don't want to go in to fight," he said.

But he says the effect of low morale will diminish as Russian troops come together to fight in larger formations, as their mission becomes clearer and as Ukrainians begin to run out of ammunition, BBC reported.