Military observers kept prisoner in Ukraine for more than a week have been released as bloody clashes in the country show no sign of letting up.
The seven observers and their five assistants, from the Organisation for Security and Cooperation in Europe, were seized in Slavyansk on April 25.
The separatists had previously accused the observers of being "Nato spies" and said they were to be used as human shields.
A prisoner-swap was thought likely, although they were set free today without any conditions.
Fresh scuffles broke out outside the burned building in Odessa on Saturday Colonel Axel Schneider, the head of the observers, said the group had shown "strength" and said the captivity was "unforgettable for us".
The release comes as Ukraine launched a dawn military operation against separatists in the east of the country.
Interior Minister Arsen Avakov said troops had seized control of a television tower in Kramatorsk, near the rebel stronghold of Slavyansk.
Two of the observers pictured while they were being held in Slavyansk "We are not stopping," Mr Avakov wrote on his Facebook page. Heavy fighting is now being reported in the town, according to Ukraine's anti-terrorist centre.
The violence comes hours after 31 people died after a building in Odessa was set on fire during clashes between protesters.
Police said some people inside the trade union building were overcome by smoke and others were killed jumping from windows as they tried to escape.
Pro-Russian and pro-Kiev activists fought running battles as the southern city saw some of its worst violence since President Victor Yanukovych was ousted in February.
Police are guarding the charred trade union building in Odessa The Interior Ministry said a total of 42 people had died.
Sky News' Katie Stallard said emotions were running high on the city's streets on Saturday as a few hundred officers guarded the charred building and people came to lay flowers.
"There is anger toward these officers. People feel they stood by yesterday; that they did very little to protect people.
"One woman told us she saw a young man and woman jump together from this building. People here witnessed something terrible last night."
A protester throws a petrol bomb at the building during Friday's clashes Russia said it was "outraged" and denounced the "criminal irresponsibility" of the pro-Western authorities in Kiev.
Russia's foreign ministry called on Ukraine and its "Western backers to end the anarchy and take responsibility for the Ukranian people".
At an emergency session of the United Nations Security Council, the UK accused Moscow of "breathtaking" hypocrisy over the latest clashes.
People wait for rescue on an upper-storey ledge during the fire The UK's ambassador to the UN, Sir Mark Lyall Grant, said Russia had "funded, equipped and directed" some of those involved in the insurgency.
"Many" pro-Russian separatists were also said to have been killed on Friday as the Ukrainian army took control of checkpoints around Slavyansk.
Two Ukrainian soldiers were also killed as two helicopters were shot down in the city, acting president Oleksandr Turchynov said.

The Ukrainian Security Service said one was shot down with a surface-to-air missile, adding that the sophisticated weapon undermined Russia's claims that Slavyansk was simply under the control of armed locals.
Sky News Chief Correspondent Stuart Ramsay, in Donetsk, said the Ukraine government is in a "very difficult position".
"If they want to take control of these towns they are going to have to put a lot of soldiers on the ground and bring in police from other parts of the country. If that happens it will absolutely be violent – it will only escalate further.
"Russia has made it clear that would be a reason for them to intervene to protect ethnic Russians.
"If Kiev doesn't do that, they are going to see the eastern parts of the country drift away."
Russia has tens of thousands of troops near Ukraine's border, and Kiev claims its neighbouring country is preparing to invade and that it is stoking the unrest in the east.
Moscow denies the allegations, but has warned Russia would respond to attacks on Russian citizens or interests in the east, where insurgents have seized government buildings in around a dozen cities.
There are fears of further landslides in the area
A digger works to clear the mud
Thousands of people have been displaced
Afghan National Army troops in Kabul load supplies for survivors
The US and the Nato-led coalition in Afghanistan have offered to send help
There have been 400 cases worldwide. Pic: NIAID
The man travelled on a British Airways plane from Saudi Arabia to Heathrow
It is thought that coronavirus may have come from camels
Low-lying areas appear in brown and elevated areas in green
A man, said to be one of the helicopter crew, is taken away
A helicopter lands at Andreevka, 7 km from the centre of Slavyansk
Ukrainian troops stand guard at a checkpoint near Slavyansk 

Clarkson with Top Gear's the Stig, Richard Hammond, left, James May, centre
The co-hosts outside Downing St in 2011
Clarkson's sillier side on show in 1998
Clarkson, Hammond and May cross Tower Bridge in 2008
Clarkson in New Zealand in 2009
The show went on tour to Belgium last year
A solemn-looking Clarkson in a video apology he posted on Twitter
Footage of Clarkson in which he is accused of using racist language
Clarkson test drives a trolley in 1997
The presenters in Amsterdam last year 
Clarkson at a film premiere in London in 2012
Mrs Maguire's family read some of the tributes to her outside the school
Mrs Maguire was stabbed as she taught at Corpus Christi Catholic College
Headteacher Steve Mort reads messages attached to bouquets of flowers
The picture Peaches posted with her mother
Smith said he lived in fear of being burgled
Hoskins, whose spanned four decades, died in hospital at the age of 71
Hoskins shares a joke with Dame Judi Dench at an LA film premiere in 2005
Ukraine's acting president Oleksander Turchinov at the cabinet meeting
The hashtag #thankyouteacher has attracted a flood of posts
Tributes have been left at the school gates as well as on social media 
One of the many handwritten tributes to school teacher Ann Maguire
Prayers were also said for the family of the boy who stabbed the teacher
The school community has been stunned by the murder of the popular teacher
Head teacher Steve Moat and students lay flowers in church
Clifford has described the charges as a 'nightmare'
The trial heard from Clifford's daughter Louise who said he was 'her rock'