Just a year ago, Ruslan, a marine in Ukraine's top battalion stationed in the Crimean port of Feodosiya, helped Russian soldiers paint their armoured personnel carrier for a military parade.

On Monday, he spotted the same vehicle being used to block the gate to his base as Russians showered its barracks with tear gas and stun grenades in a pre-dawn raid that took the unarmed Ukrainians by complete surprise.

"We thought of them as our own, as our brothers," said Ruslan, who declined to give his last name.

"We trusted them... and they trusted us," he told AFP at a Feodosiya cafe after spending hours in Russian custody.

"And now they received these orders (to attack us), and what they did was completely inhuman. It's not the Christian way."

Ruslan, who is in his late 20s, said he was torn by Moscow's seizure and annexation of Crimea as his parents live in Ukraine and his wife and children were born on the peninsula.

The Feodosiya base, where he served for six years, is one of the last Ukrainian military bases in Crimea to fall under Russian control.

But it was not the tear gas that stung these marines the most -- it was the Russians who broke a promise to allow them to leave the base peacefully on Monday in exchange for their arms.

"There was an agreement that we hand over the weapons... and at noon today we were to lower the flag and drive out on our trucks to go to the mainland. But that's not what happened," Ruslan said.

The unit locked up its armoury and handed it over -- but then was woken up by a raid at 4:00 am.

- 'They took everything' -

"They fired bullets at us while we were completely unarmed," said Yevgeniy, another marine.

"My friend had his nose broken with the butt of a rifle for nothing, he put up no resistance.

"They took our military IDs, phones, money -- everything they could lay their hands on."

The marines said that if they had known this was going to happen, they would never have surrendered their weapons.

A soldier Yevgeniy knew tied him up and loaded him onto a Ural military truck at 6:00 am.

"He said 'Sorry brother, we have nothing to do with this. The security services are at work here'."

As Russia asserts its control over Crimea, Ukrainian servicemen note the irony that many of those under attack were themselves born in Russia and felt closer to Moscow than their new government.

In the early days of the blockade, Russians besieging the base carried food parcels to the Ukrainians inside, who then frequently shared the food.

- 'No orders' -

"We resisted for 23 days on dried food, on canned fish. Could defence ministry officials have survived like that for so long?" Ruslan asked bitterly.

"They kept saying, 'Hold on... it's being decided'.

"We asked them for a command, but there was nothing."

The angry marines are ready to go straight to Kiev and raise some hell, said Yevgeniy, who is also in his late 20s.

"We'll go back to Ukraine. If nobody picks us up at the border, all of us will go to Kiev to the Rada (parliament), to the defence ministry.

"We'll storm them, and maybe then they'll treat us differently," he said as he waited for a bus to the border town of Chongar.

Ukraine should have immediately put up barriers at all Russian crossings to protect Crimea, the marines said. They think the peninsula has been lost because of poor leadership.

Former president Viktor "Yanukovych should have used troops at Maidan," Yevgeniy said, referring to the Kiev square occupied by pro-European protesters who toppled the pro-Moscow leader last month.

"He believed the wrong people... and where is he now? And where are we now? We are totally fucked."