* Two planes evacuate families bussed to Beirut
* Russia's MidEast envoy says civil war unlikely to end soon
* No sign of a shift in Russian position on Assad exit (Releads after plane take-off; adds quote from evacuee)
By Alexander Dziadosz and Alexei Anishchuk
BEIRUT/MOSCOW, Jan 22 (Reuters) - Two planes carrying around 90 Russians escaping Syria's civil war left Beirut airport on Tuesday, the Russian Emergencies Ministry said, an operation that Moscow denied was the start of a mass exodus.
"We are not talking about a full evacuation ... It is not planned that everyone will leave," Russian Deputy Foreign Minister Andrei Denisov said, according to the Itar-Tass news agency.
Russia has been President Bashar al-Assad's most powerful foreign protector during a 22-month uprising against his rule, vetoing three U.N. Security Council resolutions aimed to push him out or press him to end the bloodshed.
But President Vladimir Putin's Middle East affairs envoy was quoted as saying in December that the rebels could defeat Assad and that Russia was preparing evacuation plans in case that were needed - comments Moscow officials have sought to play down.
The same envoy, Deputy Foreign Minister Mikhail Bogdanov, said on Tuesday: "We are helping those who want to leave."
"At the beginning there were predictions (that the fighting would last) two to three months, four months," he said on the sidelines of a meeting in Moscow between Prime Minister Dmitry Medvedev and Lebanese President Michel Suleiman.
"The military-political situation could develop in various ways, but we think it (the conflict) may be prolonged."
Russian authorities declined to say why the evacuation was happening via Lebanon, but security concerns about Damascus airport may have been a factor. Rebel attacks on the airport have prompted many international airlines to suspend flights.
Dozens of Russians - many of them women and children wearing winter coats and hats - arrived at Beirut airport in large white buses, escorted by Lebanese military police. Soldiers armed with assault rifles stood by as the families unloaded suitcases onto carts.
Ammar, an 18-year-old student whose mother is Russian and father is Syrian, said family friends had taken him to the Lebanese border earlier in the day where he was picked up by the bus.
"It's a tragedy there," he said. "We hear bombs all the time. We see the MiGs and the Sukhois in the sky."
Ammar said his parents were still in Damascus waiting to finish paperwork before they left. "There's no transportation. We can't move anywhere," he said.
Russian officials say there are tens of thousands of Russian citizens in Syria, many of them Russian women married to Syrians, and their children.
Moscow leases a naval maintenance and supply facility at the Syrian port of Tartous and there are some employees from Russia's state arms exporting company Rosoboronexport. There was no indication Moscow was withdrawing any of those personnel or its diplomats.
The Emergencies Ministry said it had no information about plans for more flights, and Foreign Ministry officials have not said whether a further evacuation was planned.
Moscow says it has no intention of propping up Assad but insists he must not be pushed from power by outside forces and that his exit must not be a precondition for a peace deal.
More than 60,000 people have been killed in the Syria conflict, the United Nations estimates. (Additional reporting by Thomas Grove and Steve Gutterman; Editing by Robin Pomeroy)