An estimated 70,000 pro-Western Ukrainians thronged the heart of Kiev on Sunday vowing never to give up their drive to oust President Viktor Yanukovych over his alliance with old master Russia, AFP reports.
Opposition leaders addressed a crowd of supporters wearing blue and yellow ribbons -- the colours of both Ukraine and the European Union -- on the central Independence Square in a bid to ratchet up pressure on Yanukovych to appoint a new pro-Western government.
"None of the kidnappings and tortures have yielded any results," said Igor Lutsenko, an activist who survived a severe beating after reportedly being abducted from hospital during deadly unrest in January.
The ex-Soviet nation of 46 million people has been in chaos since November when Yanukovych ditched an historic EU trade and political pact in favour of closer ties with Moscow, stunning pro-EU parts of the population and sparking violent protests.
Since then, what started out as a localised, domestic bout of unrest has snowballed into a titanic tussle for Ukraine's future between Russia and the West, as demonstrations continued and spread to other parts of the country.
Ukraine's state security service announced Sunday that anti-terrorist units had been placed on high alert due to increased threats against key sites such as airports, stations, pipelines and nuclear plants.
The SBU counterintelligence agency said the measures were "primarily preventative" and made no explicit reference to the mass protests.
But it mentioned "threats of explosions" at strategic transport hubs and energy installations as well as "calls to occupy sites sheltering large stocks of weapons" and the "blockading of government buildings".
The protesters who have been occupying central Kiev for more than two months have seized several state buildings and repeatedly clashed with police.
Opposition must be 'resolved'
After initially ignoring protesters' demands, Yanukovych has recently yielded ground by dismissing the government. But he also has to appease Russia, which has effectively frozen a sorely-needed $15-billion (11-billion-euro) bailout until the situation clears up.
Moscow has so far issued only one $3.0-billion instalment of the loan, which it promised to Yanukovych after he rejected the EU pact.
"People must stay on the streets until the end, otherwise there will be reprisals. And the opposition must be more resolved, not limit themselves to speeches on the podium. We need early presidential elections and a new constitution," Anna Rebenok, a young secretary, told AFP on Independence Square.
The protest -- which ended without violence -- is the 10th major demonstration since November, and the size of the crowds Sunday roughly equalled the turnout last weekend, although it was markedly lower than at the end of January, when violence left several people dead and hundreds injured.
Protesters have set up row upon row of manned, grimy barricades on all four roads leading to the square, turning it into a pro-Western fortress that leaves riot police on the outside.
On an upmarket avenue near the square, protesters and curious onlookers had clambered onto one of these barricades made slippery by melting snow, facing off with dozens of riot police as a line of burnt vehicles stood in between.
One woman wore high-heels, the other carried her baby up, and many took pictures with their smartphones. Nearby, a man in army fatigues read Dan Brown's "Angels & Demons".
But this light atmosphere was darkened by the presence of men wearing bullet-proof vests and helmets and carrying batons -- members of self-defence groups patrolling an avenue that was the scene of violent clashes in January.
Klitschko challenges president
Former world champion boxer turned opposition icon Vitali Klitschko set a challenge for Yanukovych, inviting him to come to the square and face his pro-EU foes.
"I am going to suggest to him that he come here on the Maidan (Independence Square) to hear what people say about him," he told a cheering crowd.
The opposition wants lawmakers to slash presidential powers and return to a pre-2010 constitution that swayed the balance towards parliament.
They are also calling on authorities to release detained protesters. Influential pro-demonstration tycoon Petro Poroshenko told the crowd that so far, 392 demonstrators had been released and 49 were still being held.
But Sergei Guilenko, a student in Kiev, said he had heard it all before.
"Authorities can only be influenced by two things: energetic action from society and Western sanctions. The European Union must get going, hit our oligarchs and Yanukovych himself," he said.
"Then he will have to make concessions."
But Ukraine's tattered economy is in ever-growing need of assistance amid sliding domestic production and dwindling foreign reserves, which analysts say could push Yanukovych to ignore opposition demands and appoint a new pro-Moscow government.
The protracted crisis has seen Ukraine's borrowing costs spike and the currency lose nearly 10 percent of its value as frightened consumers rush to stock up on dollars and euros.