Riot police clash with protesters in Kiev after the government refuses to sign up to closer ties with the European Union.
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Police encircled the capital's Independence Square and fired tear gas to disperse crowds who had gathered to protest against President Viktor Yanukovych's abrupt decision not to sign a landmark association agreement with the EU.
There were mass protests across the former Soviet Republic, where the president's decision is widely seen as a capitulation to pressure from the country's powerful neighbour Russia.
Demonstrators in Kiev have been holding rallies for nine days to push for greater European integration. The rallies recall the Orange Revolution of 2004 which saw Mr Yanukovich's election victory overturned in favour of his pro-western opponent Viktor Yushchenko.
In Lviv, protesters waving EU and Ukrainian flags linked arms to form a human chain intended to reach across the nearby Polish border to Przemysl, the closest city in the EU.
Student Maxim Cherepaka said: "I'm for Europe. Ukraine is Europe. We've already had experience with Russia, the USSR, which we don't need to repeat."
Fellow demonstrator Orest Poddolyak said: "We want to tell the whole world that Ukrainians are a European nation, because we proclaim - and I think a lot of people here support me - that European values, a European standard of living, education, medicine, and corresponding European standards are suitable for us."
A rival demonstration in Kiev saw thousands of people bussed in from areas in the Russian-speaking east of Ukraine loyal to Mr Yanukovich to sing songs and make speeches praising closer ties with Russia.
The Russian leader, Vladimir Putin, is widely accused of trying to block the deal by banning some of Ukraine's imports and threatening more trade sanctions. Russia has squeezed gas supplies to Ukraine in the past at times of tension, forcing the country to struggle through hard winters.
The agreement at a summit in Lithuania would not have given Ukraine EU membership, but it would have opened up potentially lucrative EU markets.
Nevertheless, Mr Yanukovich is widely believed to have accepted a higher offer from Russian President Vladimir Putin than the 600 million euros put on the table by EU negotiators.
He told EU leaders in a closed summit session that "unfortunately" Ukraine was alone in dealing with "serious financial and economic problems".
The Ukrainian leader needs cash to meet debt repayments of nearly £5bn if he is to secure re-election in 2015.
Ukrainian opposition leader Arseny Yatsenyuk said: "It's clear that this president sold Ukrainian destiny and Ukrainian future in order to contain and to preserve his power and in order to grab the office of the president of Ukraine in 2015.
"And he did it under the auspices of President Putin. So this president, I mean President Yanukovich, betrayed the Ukrainian people. He sold my country. President Putin is the winner."
Opposition politician and heavyweight boxing champion Vitali Klitschko said: "Yanukovich has humiliated Ukraine. He's not interested in Ukrainian's fate - he has only his own interests at heart.
"The European leaders are very disappointed. Europe has kept the door open for Ukrainians, but I am sure this door has been closed for Yanukovich and his government."
Deal 'still on the table'
EU Council president Herman van Rompuy, EU Council President, said: "The offer of signing the most ambitious agreement the European Union has ever offered to a non-member state is still on the table.
"We have to set aside short-term considerations and we have to overcome pressure from abroad. This is a time of courage, this is a time of decisions."
Lithuanian president Dalia Grybauskaite said: "The EU remains ready to help the Ukrainian people, to assist them on their road to democracy, to human rights, where democracy and human rights will be under their own control.
"So today, we as Europeans stand together with the Ukrainian people. The door to the European Union to a deeper integration with the EU is open to the entire Ukrainian society. Everything depends on the political elite now. This political elite, the Ukrainian government might change their decision."
Some Ukrainians remain hopeful that closer integration will go ahead, noting that Mr Yanukovich had suspended plans to sign the deal, not cancelled them altogether.
No 'veto' for Russia
EU Commission President Jose Manuel Barroso said: "We will not give in to external pressure, not the least from Russia.
"What we cannot accept is a condition on a bilateral agreement to have a kind of a possible veto of a third country. This is contrary to all principles of international law."
Polish President Bronislaw Komorowski said: "The problem is the policy of pressure and blackmail employed towards Ukraine by its eastern neighbour."
The EU did manage to extend its sphere of influence eastward into the former Soviet bloc by initialling agreements with Moldova and Russia's neighbour Georgia. But Ukraine and Armenia have rejected advances from the customs union.
Mr Putin is known to favour the creation of a Eurasian union, a separate trading block taking in former Soviet states that would stretch from the borders of China to western Europe.
Last week the Russian president accused EU states of issuing threats to help organise demonstrations in Ukraine, saying: "Whether Ukraine and the Ukrainian government will give in to this blackmail, or whether it will be able to with stand it and make a decision based upon the national interests of the country, we will find out in the next few days."
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