* Flame journey is longest in Winter Games history
* Concerns over anti-gay propaganda law and security (Adds quotes, details)
By Karolos Grohmann
ANCIENT OLYMPIA, Greece, Sept 29 (Reuters) - The Sochi 2014 Winter Olympic torch was lit in ancient Olympia on Sunday heralding the start of what will be the longest torch relay for any Winter Games, including a trip to space, as Russia prepares to showcase its modern post-Soviet face.
The Black Sea resort of Sochi, the first Russian city to stage a Winter Olympics, will receive the flame on Oct. 5 after a short relay in Greece, to kick off a 123-day odyssey culminating at the opening ceremony on Feb. 7.
Russian President Vladimir Putin is eager to deliver a "brilliant" Games to show how far Russia has come since the collapse of the Soviet Union in 1991.
On a hot autumn day, Greek actress Ino Menegaki, playing a high priestess, lit the torch in seconds as the sun's rays bounced off a concave mirror at the birthplace of the ancient Olympics, a ritual first established for the 1936 Berlin Games.
"I hope the Games show the world that Russia is not only salt cucumbers and vodka," Denis Kruzhkov, 40, a university professor from a town near Sochi, told Reuters.
Wrapped in a Russian flag on the green slopes hugging the ancient stadium, he said: "I hope Sochi represents the new Russia. Sochi is multi-national and safe, and sport unites people."
After leaving Greece, the flame will travel to outer space, the bottom of Lake Baikal, the North Pole and Europe's highest peak in the mammoth trek across the vast country, carried by a record 14,000 torch-bearers.
"This is the beginning of an epic journey for the Olympic torch," Sochi Games chief Dmitry Chernyshenko said. "A journey that will change Russia forever."
It will not be plain sailing for the Russian organisers until the Games opening, however, with mounting international criticism over a new anti-gay propaganda law which critics believe is repressive.
Security in the city near the volatile North Caucasus region is also a major concern with Putin saying more needed to be done.
On Friday Russian security forces killed five suspected militants in the North Caucasus province of Agestan, including one believed to be a local Islamist insurgent leader.
"Just as in ancient Greece, the Olympic Games cannot settle political problems or secure lasting peace between peoples," new International Olympic Committee (IOC) President Thomas Bach said in a brief speech from the ruins of the ancient stadium.
"The Olympic flame thus reminds us to be aware of our own Olympic limits."
Human rights groups and some athletes have criticised the IOC for failing to do more to press Russia over the new law.
"The IOC is not meant to be a government who imposes laws and regulations," Bach told Reuters after the ceremony, conducted amid an unusually small crowd of spectators and draconian security measures, including hundreds of police on the ground and helicopters clattering overhead.
"The IOC is not a supra-national parliament or government which can impose laws outside the Olympic Games on a sovereign country.
"But we are very clear that we will not tolerate any form of discrimination. The task of the IOC is that the Olympic Charter is applied 100 percent," Bach said on his first official assignment since succeeding Jacques Rogge.
Ice hockey player Alexander Ovechkin was the first Russian to run with the torch after Greek Alpine skier Ioannis Antoniou kicked off the relay.
It will eventually travel across 83 regions in Russia and 2,900 settlements on its 65,000 kms route through the world's largest country. (Additional reporting by Karolina Tagaris in ancient Olympia; Editing by John O'Brien)