KIEV  - Anti-government protesters were locked in a stand-off with riot police across burning barricades Wednesday after fierce clashes left at least 26 people dead in Ukraine’s worst crisis since the collapse of the Soviet Union.

The European Union called an emergency meeting to discuss sanctions against those behind the deadly unrest, as embattled President Viktor Yanukovych blamed the opposition for the biggest escalation of violence yet in three months of protests. Ukrainian President Viktor Yanukovych on Wednesday replaced the head of the army’s general staff after announcing a new “anti-terror” operation in response to the country’s deadliest violence since its post-Soviet independence.

A brief presidential statement said Yanukovych was appointing Yuri Iliin in place of Volodymyr Zamana to head the powerful post but provided no explanation for the decision.

Security forces on Kiev’s Independence Square appeared to have temporarily halted their push to take over the city’s main protest camp as people from around Kiev streamed to the site with food, clothing and medication for the demonstrators.

Some protesters on the smoke-filled square hurled Molotov cocktails and cobble stones at the lines of riot police, while others piled wood onto the burning barricades separating them from the security forces.

Riot officers responded with the odd volley of stun grenades and rubber bullets. They also used a water cannon to douse protesters and put out the occasional fire.  Despite the tensions, the scene was more subdued than on Tuesday, when riot police stormed the protest square, leading to apocalyptic scenes that triggered international condemnation.

At the Winter Olympic Games in Sochi, shocked Ukrainian athletes wanted to wear black armbands to mourn the dead, a request that was denied by the International Olympic Committee as it would interfere with rules on athletes’ clothing.

Tuesday’s unrest in Kiev was the deadliest since protests erupted in November after Yanukovych rejected an EU pact in favour of closer ties with Moscow.

Since then, the crisis has snowballed into a titanic tug of war for the country’s future between Russia and the West.

In response to the deadly clashes, EU foreign policy chief Catherine Ashton summoned the bloc’s foreign ministers for emergency talks on Ukraine on Thursday, with sanctions against leading figures being considered.

“All possible options will be explored, including restrictive measures against those responsible for repression and human rights violations,” she said.

Calls for sanctions were echoed by France and Poland, while US Vice President Joe Biden urged Yanukovych in a phone call to “pull back government forces and to exercise maximum restraint”. Germany meanwhile blamed the worsening crisis on Yanukovych’s refusal to engage in serious dialogue with the opposition. But in a televised address to the nation as the clashes raged, a defiant Yanukovych accused the opposition of undemocratic behaviour.

“The leaders of the opposition... have crossed the limits by calling for people to take up arms,” Yanukovych said.

Russia, which offered debt-laden Ukraine a $15 billion bailout after Yanukovych spurned the EU pact and has repeatedly condemned Western interference in the Ukrainian crisis, described the protests as “an attempted coup d’etat”.

The Ukrainian security services later said they were launching a probe into an attempted coup. Late night talks on Tuesday between Yanukovych and the opposition failed to go anywhere, prompting opposition leaders to call on protesters to stand their ground on the Maidan, as Independence Square is known.

“This is a small island of freedom,” opposition leader and former boxing champion Vitali Klitschko said after the talks, adding that the protesters were “not going anywhere”.

Kiev was effectively in lockdown on Wednesday as authorities shut down the city’s metro system and limited traffic into the capital. Schools in the centre were closed.

Ukraine’s health ministry said 26 people had died in the clashes since Tuesday morning, including 10 policemen. The injured included 263 protesters and 342 police.

A journalist working for a pro-government Kiev newspaper died of gunshot wounds after he was shot by masked men, his newspaper Vesti said.

The interior ministry said that 58 people had been detained over the fighting in Kiev.

Yanukovych called for a day of mourning on Thursday.

The latest outbreak of the violence surprised many, as tensions appeared to have been subsiding in recent days with both sides making concessions that saw protesters vacate Kiev city hall on Sunday after being granted an amnesty deal.

But on Tuesday, anti-Yanukovych protesters clashed with police outside parliament as they rallied for lawmakers to strip the president of a raft of powers.

Running street battles broke out, as protesters re-occupied city hall and attacked Yanukovych’s party headquarters with petrol bombs.

Police descended on Independence Square in the evening, warning women and children through loudspeakers to leave as they began their “anti-terrorist” operation.

But some 25,000 people, many of them wearing makeshift body protection and wielding iron bars and bats, remained to battle the riot squads.

The violence also spread to the west of the country, where thousands of protesters overran public buildings, including the police and special forces’ headquarters in the historic city of Lviv, where they took control of an arms warehouse.

In Ternopil, protesters lobbed Molotov cocktails at a local government building before occupying it, while similar scenes played out in the city of Ivano-Frankivsk.