* Medvedev met opposition leaders, first time since big protests
* Activists say meeting brought no immediate results
* Putin expected to win March 4 presidential election (Updates throughout with meeting, quotes)
By Alexei Anishchuk
MOSCOW, Feb 20 (Reuters) - A rare meeting between Russia's president and opposition leaders produced talk of political reform on Monday but no sign of concessions strong enough to halt protests posing a challenge to Vladimir Putin as he prepares to return to the Kremlin.
President Dmitry Medvedev hosted protest organisers and leaders of unregistered parties at his residence outside Moscow in the first known direct high-level contact between the opposition and the Kremlin since the protests began in December.
"Our political system is far from ideal, and the majority of those present here criticise it, sometimes quite harshly," Medvedev, said in televised comments at the meeting.
"You know that for the last four years I have been changing certain parts of our political system. At the moment, in my view, the time has come to do this more actively," said Medvedev, whose term ends in early May.
Medvedev said he welcomed suggestions on how electoral reform legislation he has submitted to parliament since the protests began, including easier registration for parties and a return to elections of regional leaders, could be improved.
The meeting signaled an awareness of the challenge Putin, now Russia's prime minister, faces from the protests as he prepares to reclaim the presidency from Medvedev, the protege he ushered into the Kremlin in 2008 when he faced a bar on a third straight term.
Tens of thousands have turned out for opposition protests three times since a Dec. 4 parliamentary election, venting anger over suspected fraud in his party's favour and calling for a "Russia without Putin".
Putin, 59, is almost certain to win the presidency but the protests have revealed discontent among middle-class Russians who want change.
Shown prominently on state television, Monday's meeting also allowed the Kremlin to portray itself as inclusive and sensitive to the concerns of some of Putin's fiercest critics, such as former Deputy Prime Minister Boris Nemtsov.
Nemtsov said he had conveyed the demands of the protesters to Medvedev, including calls for the release people they say are political prisoners, such as former oil tycoon Mikhail Khodorkovsky, jailed since 2003 and due out in 2016.
"We can only talk about the results of this meeting when these people are free," Nemtsov said. "Only then I would feel that the contact wasn't in vain."
Nemtsov said Medvedev's reaction to his proposal to limit total number of presidential terms one person could serve to two was surprisingly positive.
But no concrete plans for that or any other political reform beyond the changes already promised emerged from the metting.
Liberal former lawmaker Vladimir Ryzhkov, another protest leader, said Medvedev appeared determined to get the political reform bills he has submitted passed before his term expires.
"He is ready to improve these draft bills, he is against spoiling them," Ryzhkov said on state-run First Channel TV.
In addition to restoring elections of governors, which Putin scrapped during his presidency, the bills would make it easier for political parties to register and contest elections, and would change the rules for parliamentary elections.
Some Kremlin critics have ridiculed the reform bills as too little, too late, and many fear Putin's party, which dominates parliament despite losing seats in the December vote, will shape them to his own benefit and to Putin's.
Putin has ignored most of the protesters' demands - including a rerun of the parliamentary election - and mocked them by likening the dissenters to apes and comparing the white ribbons worn by them to condoms.
Opposition figures seen as more radical by the Kremlin, such as anti-corruption blogger Alexei Navalny, did not attend Monday's meeting. (Reporting by Alexei Anishchuk; Editing by Timothy Heritage and Steve Gutterman)