Ukraine: Deadly clashes around parliament in Kiev
Violent clashes have erupted during anti-government protests in Ukraine's capital, Kiev, with at least nine people, including two policemen, dead.
In the worst violence in weeks, police used rubber bullets and stun grenades as thousands of protesters marching on parliament.
A deadline set by the security forces for the violence to end has passed with no immediate sign of police action.
The clashes came as MPs were due to debate changes to the constitution.
The proposals would curb the powers of President Viktor Yanukovych, but the opposition say they were blocked from submitting their draft, meaning no debate could take place.
EU foreign policy chief Catherine Ashton said she was "deeply worried" by the escalation of violence, and urged politicians to "address the root causes".
Russia blamed the upsurge in violence on "connivance by Western politicians and European structures" and their refusal to consider the "aggressive actions" of radical factions within the protest movement.
Officer shot dead
Ukraine's unrest began in November, when Mr Yanukovych rejected a deal with the EU in favour of closer ties with Russia.
The mood had calmed in recent days, but protest camps remain on the streets and the opposition - which insists the president must resign - had warned the government it risked inflaming tensions if it failed to act.
On Tuesday, thousands of protesters tried to march on the parliament building to put pressure on the government to address constitutional reform. But the march was blocked by lines of police vehicles.
The BBC's David Stern in Kiev says it is unclear what sparked the clashes - protesters and police have blamed each other.
Unlike in previous weeks, violence took place in a number of locations, our correspondent adds.
Some protesters ripped up cobblestones to throw at police. Others threw smoke bombs. Police fired stun and smoke grenades, and rubber bullets.
Protesters also attacked the headquarters of President Yanukovych's Party of the Regions, temporarily smashing their way in and setting it on fire before being forced out by police.
One person - believed to be an employee - was found dead inside.
The bodies of three protesters were found inside a building close to parliament. Another three bodies were seen lying in the street.
The interior ministry said two policemen had died of gunshot wounds.
Dozens of protesters and security personnel are also reported to have been injured.
The heads of the security services and internal affairs ministry gave the protesters a deadline of 18:00 local time (16:00 GMT) to put an end to the clashes, warning they would "use all the possible methods" to end it.
The entire Kiev metro has been shut down, and police have converged on the edges of Independence Square, the site of the main protest camp since November.
Protest leader Vitaly Klitschko urged women and children to leave the square, saying they could not "exclude the possibility of use of force".
But the deadline came and went with no apparent sign of security force action.
Inside parliament on Tuesday morning, there were scuffles as the opposition tried to submit a draft resolution on reinstating the 2004 constitution.
The changes would mean President Yanukovych losing some of the powers he has gained since his election in 2010, including the power to appoint the prime minister and most cabinet members. They could also lead to snap presidential elections.
Opposition leader Arseniy Yatsenyuk said the move was being blocked by President Yanukovych, saying his party members "show no desire whatsoever to end the political crisis".
MPs who support the president say the proposals have not been thoroughly discussed, and that more time is needed.
The speaker of parliament, Volodymyr Rybak, said parliament would not meet on Wednesday, but that opposition leaders would meet the president for further talks.
Several countries have expressed their alarm and concern at the sudden escalation of the crisis.
- The US's National Security Council said it was "appalled by the violence" and urged President Yanukovych to "immediately de-escalate the situation and end the confrontation"
- German Foreign Minister Frank-Walter Steinmeier called on both sides to "return urgently" to their attempts to find a political solution.
- The UK's Minister for Europe David Lidington said such violence had "no place in a European democracy" and urged "all parties to return to the path of compromise and genuine negotiation".
- Poland's foreign ministry said it had summoned Ukraine's deputy ambassador to express its concern, and called for "immediate dialogue".