KAZAN, Russia - U.S. Secretary of State Hillary Clinton wrapped up a European tour Wednesday by calling on Russia to uphold human rights and prevent attacks on activists who challenge the Kremlin.

Clinton devoted the second day of her Russia visit to events with ordinary citizens, following a round of diplomacy with Moscow officials which produced warm words from both sides about cooperation but no specific results.

People must be free to take unpopular positions, disagree with conventional wisdom, know they are safe to peacefully challenge accepted practice and authority, she said in a speech at Moscow State University.

That's why attacks on journalists and human rights defenders here in Russia is such a great concern because it is a threat to progress, Clinton said.

As Clinton spoke, Russian opposition lawmakers walked out of parliament in protest against regional elections Sunday in which Prime Minister Vladimir Putin's ruling United Russia party won victories across the country.

Some opposition leaders said they would boycott parliament until President Dmitry Medvedev agreed to meet them to discuss claims of vote-rigging. U.S. officials traveling with Clinton said they did not want to comment on internal Russian issues.

Clinton later flew east to meet one of United Russia's leaders, Tatarstan Governor Mintimer Shaimiyev, in the ancient city of Kazan. Dressed in a yellow headscarf, she toured a mosque and a Russian Orthodox cathedral in the mainly Muslim region.

I appreciate the outreach you are doing to the Islamic world and to Europe and other places to serve as a model and a bridge between the worlds of Islam and Christianity, Clinton told Shaimiyev.

IRAN, HUMAN RIGHTS

U.S. President Barack Obama has called for a reset in ties with Russia and its people after the rows which dominated the relationship under his predecessor, George W. Bush.

But some rights activists fear Washington could tone down public criticism of the Kremlin in return for Moscow's cooperation on Afghanistan or Iran.

Clinton's criticisms of Russia on rights and democracy were made at two meetings with citizens which were not carried by state-run television while at her joint news conference with Lavrov she avoided harsh words.

At talks with Medvedev Tuesday, Clinton failed to secure support for tougher sanctions on Iran despite Obama's decision to scrap Bush-era plans for a missile shield in central Europe -- a concession to Russian concerns which Washington had hoped might spur Moscow to back its position on Iran.

I believe if sanctions become necessary we will have support from Russia, Clinton told ABC television in an interview. I'm very pleased about how supportive the Russians have been in what has become a united international effort.

On the issue of missile defense -- which had been the most contentious issue between Moscow and Washington in the Bush era -- there were few specifics during Clinton's visit.

Lavrov said he was still waiting hear more details about Obama's revised proposals, which envisage a mobile system using ships, and a Russian deputy minister said Moscow and Washington needed to agree first on where the missile threats were before they could think about cooperating.

Clinton said she had wished to meet Russia's key decision maker, Prime Minister Vladimir Putin, but he was on an official visit to China during her time in Moscow.

Clinton, taking questions from the Moscow students, said some officials in both countries were still mired in the Cold War and viewed each other as enemies.

We have people in our government and you have people in your government who are still living in the past, Clinton said.

They do not believe that the United States and Russia can cooperate to this extent. They do not trust each other. And we have to prove them wrong.

(Writing by Guy Faulconbridge and Conor Sweeney; editing by Angus MacSwan)