* Riot police move into square, held back by protesters
* Kerry, EU foreign policy chief denounce police move
* Opposition's Klitschko calls for president to go (Adds comments by Klitschko, protesters)
By Alissa de Carbonnel and Pavel Polityuk
KIEV, Dec 11 (Reuters) - Ukrainian riot police cleared streets near a protest camp overnight and entered the occupied Kiev City Hall on Wednesday, where demonstrators sprayed them with water hoses to prevent the building from being stormed.
The overnight moves by hundreds of black-clad police with visors and helmets were the biggest step the authorities have taken so far to disburse weeks of protests against President Viktor Yanukovich, although it was not clear whether they were prepared to use full force.
At the main protest camp on Independence Square, pop stars, politicians and priests pleaded with police not to shed blood. Opposition politicians called for mass demonstrations to protect the square and predicted that Yanukovich would soon be toppled.
The interior minister called for calm and said the square would not be stormed.
Overnight, police cleared demonstrators from roads leading to the camp but did not force them out of the square. More police were bussed in to shouts of "Get out criminal" - a reference to Yanukovich, who suspended plans to sign a trade pact with the European Union last month.
Some protesters said police had moved into City Hall, the headquarters of the Kiev municipal administration which the demonstrators have occupied for more than a week and are using as a makeshift hospital. It was not clear how many police were inside. The besieged protesters turned water hoses on them.
The police moves began in darkness near Independence Square, where thousands of protesters have maintained a vigil in bitter winter cold against Yanukovich's Nov. 21 decision to embrace closer ties with Russia instead of the EU.
Riot police flooded roads to square and moved slowly into the main camp, tearing down some of the barricades.
Dozens of demonstrators and police were hurt in scuffles but several officers said they had orders not to use force. As day broke, with temperatures in the snowbound capital stuck at minus 8 degrees Celsius (17 Fahrenheit), some riot police left to cheers from lines of protesters holding them back.
Many protesters said they had feared they would be stormed. Priests intoned prayers from a stage on the square and urged police not to use violence. Ruslana, a Ukrainian pop star, called from a loud hailer: "Do not hurt us!"
Some protesters held mobile phones in the air like candles and sang the national anthem, while church bells rang out from a cathedral about 2 km (about 1 mile) away, as in times of danger centuries ago.
"It is the stupidest thing that he could have done," said Vitaly Klitschko, a world heavyweight boxing champion turned opposition politician. "There are laws of physics: the more pressure, the more resistance. I am sure there will be a huge number of Ukrainians here in a few hours."
Another opposition leader, former economy minister Arseny Yatsenyuk said: "He (Yanukovich) is spitting in the faces of the United States, 28 countries of Europe, 46 million Ukrainians. We will not forgive him this. Tomorrow there will be a million people here and his regime will fall."
U-TURN ON EUROPE
European leaders say the trade pact with Ukraine would have brought investment. But the country's Soviet-era industry relies on Russian natural gas, giving Moscow enormous leverage.
Prime Minister Mykola Azarov said on Wednesday he had told European leaders they would need to provide Kiev with 20 billion euros in aid for Ukraine to sign the stalled pact with Brussels. He promised that a meeting with Russian officials set for Dec 17 would not include talks on joining a Moscow-dominated customs union, a main fear of the opposition.
Western countries spoke out strongly against use of force.
"The United States expresses its disgust with the decision of Ukrainian authorities to meet the peaceful protest in Kiev's Maidan Square with riot police, bulldozers, and batons, rather than with respect for democratic rights and human dignity," U.S. Secretary of State John Kerry said in a statement. "This response is neither acceptable nor does it befit a democracy."
With EU foreign policy chief Catherine Ashton and U.S. assistant secretary of state Victoria Nuland in Kiev, protest speakers urged the West to support them in a struggle which has developed into a campaign to force Yanukovich's resignation.
"Europe, do you hear us? We are standing here for our rights. We want to be independent. We don't want to go to Russia. Please do support us," said Lesya Orobets, a member of parliament.
There were signs that the authorities were reluctant to order bloodshed on the square. Interior Minister Vitaly Zakharchenko issued a statement calling for calm.
"I want everyone to calm down. There will be no storming of the square. No one will violate your rights to protest peacefully, but do not ignore the rights ... of other citizens."
The EU's Ashton, expecting to meet Yanukovich on Wednesday, said in a statement: "I observe with sadness that police use force to remove peaceful people from the centre of Kiev. The authorities did not need to act under cover of night to engage with society by using police." (Writing by Richard Balmforth and Elizabeth Piper; Editing by Peter Graff)