His eyes glazed and his step heavy, former Ukrainian soldier Sergei walks out of a naval office in Sevastopol after switching allegiance to the Russian army.

He is one of many making the choice to stay on in Crimea where the Ukrainian army stood by helplessly as Russia seized its military facilities in a matter of days after the peninsula voted to secede.

"I've decided to stay. I have my parents here, my wife's parents and my children," the grizzled soldier says softly.

He describes how he and his colleagues waited in vain for 17 days for orders from Kiev as their bases were surrounded by Russian troops and pro-Russian militia which moved in swiftly after Ukraine's government fell.

But the new leaders who ousted pro-Kremlin president Viktor Yanukovych in a street revolt were impotent as Moscow muscled its way into the strategic Black Sea peninsula and backed the March 16 breakaway vote.

The waiting troops stormed the naval headquarters last Wednesday after Crimea voted overwhelmingly in favour of the split.

"We were picked like ripe fruit," Sergei said angrily.

"If the Ukrainian army does nothing, it's not a difficult choice to quit it!"

For him the whole institution was badly managed, with rampant nepotism and "special favours" making it hard to carve out a successful career.

But he said he still loved Ukraine.

"It's my native country," he said, pausing to fiddle with his gold wedding ring before admitting: "I'm a little afraid of the reaction from Ukrainians. Many of them will take a long time to understand what we went through."

Behind him a young soldier in an oversize camouflage uniform is posted at a big metal door, checking the IDs of the steady flow of people going in to renounce their military affiliation with Ukraine.

-'Sticks and stones'-

Clutching his car keys, Oleg, a former mechanic with the Ukrainian army, said signing up to the Russian army was a "very emotional" decision.

"The Ukrainian army no longer exists. So what else would you have me do?" he said.

On leave after the Russian takeover, Oleg is now waiting for an "offer" of employment, which could take a few days.

Despite his sadness at his decision, he feels it is "impossible to leave" like those who have chosen to return to an uncertain future in mainland Ukraine.

"If I leave Crimea, I will be leaving for nothing," he said. His life is in Sevastopol, whatever flag it flies.

Most of the Ukrainian servicemen who have turned up are in their early twenties. They come in groups of three or four in jeans and sneakers, wearing sunglasses against the bright spring sun in the Black Sea peninsula.

"It was my family's choice," Alexander, a bearded 23-year-old driver, says of his decision to defect.

However the circumstances of his unit's takeover did not go down very well with the tattooed young man, who said he feels "betrayed" by Ukraine.

"We were told not to fight and not to provoke them (Russians)," said Alexander.

"When we no longer had weapons, they told us - 'Please go and fight with what you have, sticks, stones, and whatever else'.

"How was it possible to fight the tricolour (Russian flag), against our military friends who serve just on the other side of the border?" he said.