* Move announced after weeks of Russian pressure on Ukrainian bases
* Turchinov says Russian forces threatened servicemen and their families
* Troops make emotional farewell as pull-out begins
* Russians use helicopters, stun grenades, machine guns to take marine base (Adds detail of troops withdrawing)
By Aleksandar Vasovic and Gabriela Baczynska
FEODOSIA/SIMFEROPOL, Ukraine, March 24 (Reuters) - Ukrainian troops and their families began evacuating from Crimea on Monday, as Kiev effectively acknowledged defeat by Russian forces who stormed one of the last of their remaining bases on the peninsula.
Thousands of Ukrainian troops have been besieged on bases in Crimea, offering no armed resistance but refusing to surrender, since President Vladimir Putin declared Moscow's right to intervene at the start of the month.
On Monday, bowing to the reality on the ground, Kiev's leadership announced Ukrainian forces were being pulled out to spare them and their families further Russian threats. A few hours later many were already on their way out.
Scores of troops from a marine base seized earlier in the morning gathered, some with their families, at an assembly point about 1000 metres (yards) away. Most were in combat uniform, wearing trademark black berets with Ukrainian cockades depicting a winged anchor and sword. Some were in civilian clothes.
"Yesterday we had an agreement: we would lower our flag and the Russians would raise theirs. And this morning the Russians attacked, firing live ammunition. We had no weapons. We did not fire a round," said one marine, Ruslan, who was with his wife Katya and 9-month-old son.
Troops hugged each other in farewell. Some chanted "Hurra! Hurra!" in defiance. One marine in full uniform who declined to identify himself wept and blamed the government in Kiev for the chaotic end to the standoff.
"This is all Kiev's fault. We are defeated. We suffered and ministers in Kiev did not bother to issue us a proper order," he said. "They smeared our flag and honour."
As two military trucks, a bus and 10 civilian cars pulled out of the gates, servicemen shouted through the open windows of the bus: "Long live the marines."
Moscow formally annexed Crimea last week and its forces have been seizing the last Ukrainian bases in recent days.
"The National Defence and Security Council has instructed the Defence Ministry to carry out a re-deployment of military units in Crimea and evacuate their families," Ukraine's acting president Oleksander Turchinov told parliament in Kiev.
The move, he said, had been made following threats by Russian forces on the lives and health of Ukrainian service staff and their families.
Earlier on Monday Russian forces, using stun grenades and machine guns and backed by two helicopters, swept into the marine base in the port of Feodosia, overrunning one of Ukraine's last symbols of resistance. Ukrainian officers were taken away for questioning, Ukrainian officials said.
Ukrainian flags were taken down inside the base after the assault, which used similar tactics to those used to take Ukraine's Belbek air base in Crimea on Saturday.
Russia's seizure of Crimea after the ousting of Ukraine's pro-Russian president by mass protests in Kiev has triggered the worst East-West crisis since the Cold War.
Moscow formally annexed Crimea on March 21, five days after newly-installed pro-Russian leaders held a referendum which yielded an overwhelming vote to join Russia. The West and Kiev say the referendum was illegal and the result a sham.
Russian forces had seized part of the Feodosia base, used by the 1st Separate Marine Battalion, Ukraine's top military unit, earlier this month, while the Ukrainians had kept control of the armoury, the barracks and other facilities.
Turchinov, putting a brave face on Ukraine's inability to defend its bases, said Ukrainian troops' refusal to surrender in Crimea had bought valuable time for the armed forces to re-group nationally to protect the rest of Ukraine.
"Despite the huge losses, Ukrainian forces in Crimea have fulfilled their duty. They provided the ability and time for the Ukrainian armed forces to be able to ensure defensive preparations and for partial mobilisation to be organised."
In Kiev, a senior military official said the evacuation would affect about 15,000 service personnel, together with their families.
During the assault on the base in Feodosia, a Ukrainian army officer, First Lieutenant Anatoly Mozgovoy, told Reuters by phone from inside the compound that the Russians had fired shots while the Ukrainian soldiers were unarmed. Asked if the base had been taken over, he said: "Yes".
"The interior of the compound is full of Russian troops," Vladislav Seleznyov, a Ukrainian military spokesman in Crimea, said earlier. The Ukrainian Defence Ministry said Russians had driven away with Ukrainian marines in trucks from the base.
"Currently, between 60 and 80 Ukrainian marines are detained and in practice held captive by the Russian military on the territory of the Feodosia sea port. They are subject to constant psychological pressure," the ministry said,
Two days after the earlier Belbek storming, the commander of the airbase, Colonel Yuliy Mamchur, had yet to be freed. His aides believe he is being held in the Russian Black Sea Fleet's home town of Sevastopol.
Ukrainian forces have also abandoned a naval base after attacks by pro-Russian protesters, and had to surrender two flagship vessels to Russian forces over recent days as Moscow solidified its grip on Crimea. (Writing by Richard Balmforth; Editing by Peter Graff)