PRAGUE (AP) -- Hundreds of protesters carried an effigy of Uncle Sam and staged a mock trial of U.S. President George W. Bush in demonstrations against his visit here and U.S. plans to build a missile defense system.

Chanting "Shame on Bush!" and waving cardboard rockets, they rallied peacefully on a square near the medieval Prague Castle on Monday.

Growing displeasure over the U.S. drive to put a radar system in the Czech Republic and 10 interceptor missiles in neighboring Poland has overshadowed Bush's stop en route to the G8 summit in Germany.

Opponents contend the shield could make Czechs a target for terrorists and re-ignite Cold War-era tensions between Washington and Moscow.

"We had Russian troops here for more than 20 years, and I was against that, too," said Karel Janko, 63, a businessman protesting what he called "America's misguided motives" behind the missile shield. Communist youth staged a separate demonstration that began outside the U.S. Embassy, where activists held signs that read "Bush: World Hate Tour 2007." Later, they marched to the hilltop castle, where masked anarchists held banners that said "Terrorist Alert: Bush is Armed and Dangerous."

Polls say that more than 60% of Czechs oppose the idea of hosting the radar system, which would be built inside the sprawling Brdy military zone southwest of Prague, and surveys in Poland suggest just one in four Poles wants the missiles.

Opposition is growing despite repeated U.S. assurances that the rockets wouldn't carry warheads and would be purely defensive, posing no threat to Russia. "Dear Mr. President, we would like to welcome you in Prague. But don't expect everyone will be happy to meet you," the mass-circulation daily Blesk wrote in an open letter to Bush on Monday. "You are coming here to defend your radar, which most of the Czech people don't wish to have."

"We are unable to face the new threats and risks that endanger the free world alone. We are unable to face them without adequate means of defense," Czech President Vaclav Klaus wrote in a commentary for Monday's editions of the Lidove Noviny newspaper.

"I think Bush is immoral, …” said Margaret Johnova, 24, a university student who joined Monday's protests.

Underscoring Czech displeasure with Bush, the local office of the human rights group Amnesty International was collecting signatures Monday on a letter calling on him to close the U.S. terror detention facility at Guantanamo Bay, Cuba.

"It is high time to put an end to discriminatory anti-terrorist measures and respect human rights," the group said. -------------------Russia warns U.S. about missile system

President Vladimir Putin warned that Moscow could take "retaliatory steps" if Washington proceeds with plans to build a missile defense system for Europe.

In an interview released Monday, Putin suggested that Russia may respond to the threat by aiming its nuclear weapons at Europe.

"If a part of the strategic nuclear potential of the United States appears in Europe and, in the opinion of our military specialists, will threaten us, then we will have to take appropriate steps in response. What kind of steps? We will have to have new targets in Europe," Putin said, according to a transcript released by the Kremlin. These could be targeted with "ballistic or cruise missiles or maybe a completely new system" he said.

Putin told reporters that he hoped U.S. officials would change their minds regarding the missile plan, warning that Moscow was preparing a response.

"The strategic balance in the world is being upset and in order to restore this balance without creating an anti-missile defense on our territory we will be creating a system of countering that anti-missile system, which is what we are doing now," Putin said.

Relations between Moscow and Washington have soured in the past year. The two former Cold War foes are at odds over Washington's missile plans, over Russia's conflicts with former Soviet nations — including Ukraine, Georgia and Estonia — and over U.S. concerns of democratic backsliding in Russia. The White House has made no comment on Putin's new warning.

Putin gave a stinging critique of the U.S. and European powers.

"We look at what has been created in North America — horror, torture, homelessness, Guantanamo, detention without courts or investigation," Putin said.

Putin, who is nine months from the end of his second and final four-year term in office, also said Russia's presidents should serve longer terms. Immensely popular with voters — he was re-elected in 1994 with more than 71 percent of the vote — Putin has consistently rejected changing the law to allow him a third consecutive term. "Four years is a fairly short time," Putin said according to the transcript. "It seems to me that in today's Russia five, six or seven years would be acceptable, but the number of terms still should be limited."