* Reports of dead in Ukraine clashes hard to corroborate
* Critics accuse Kremlin of deploying propaganda
* Deaths of pro-Russians could trigger Moscow's intervention
* Russia says Western media censoring Kremlin's position
By Alissa de Carbonnel and Gabriela Baczynska
MOSCOW/KRAMATORSK, Ukraine April 17 Around 6:00 p.m. local time on Tuesday, Vladimir Maximovich heard the news that was ricocheting around Russian media and online: at least four pro-Russian activists had been killed and others wounded by Ukrainian troops at an airfield near the Ukrainian city of Kramatorsk.
As the head of the emergency unit at the city's public hospital, he got ready to receive the injured and treat them. They never showed up.
"We were sitting here, all of us, and waiting. We heard about the trouble at the airfield, so we were ready. But nobody came," he told Reuters on Wednesday. "I called my colleague at the surgery unit: also nothing."
The doctor had just witnessed a phenomenon that is growing familiar in the crisis over Ukraine: a dramatic assertion in Russian media about wrongdoing perpetrated by Kiev's Western-backed rulers against pro-Russian protesters, which later turns out, at best, to be based only loosely on fact.
It is an issue that has far-reaching implications. Twice in the past six years - in ex-Soviet Georgia in 2008 and in Ukraine's Crimea Peninsula earlier this year - Russia has sent its troops into a neighbouring country, arguing that it had to act to protect its Russian kin from violence.
That shadow hovers now over Ukraine, where armed pro-Russian separatists have seized buildings in around 10 towns and the Kremlin says Moscow has the right to intervene to protect Russian speakers if there is violence.
Russia has massed thousands of troops on its border with Ukraine. It says they are on routine exercises but Kiev and some of its Western allies call it an invasion force waiting for a pretext to advance.
In what appears to have been the bloodiest incident so far, Kiev said on Thursday three separatists were killed while trying to storm a national guard base in the eastern port of Mariupol overnight.
Ukraine has so far taken only limited action against the separatists. An operation by paratroops to retake some territory ended in disarray on Wednesday when rebels seized six of their armoured vehicles and another column surrendered the firing pins of their rifles and retreated rather than open fire.
The media storm over the purported killings on Tuesday in Kramatorsk petered out, and Russian forces on the border have so far stayed put.
But the way the accounts of the casualties in the city originated, then snowballed, is telling because it is a scenario that could be repeated as forces loyal to Kiev try to reassert their authority over pro-Russian rebels.
On Tuesday, a Ukrainian army unit landed by helicopter at the airfield near Kramatorsk in eastern Ukraine, a location which a short time earlier had been controlled by protesters backing a pro-Russian separatist movement.
A Reuters reporter at the scene said there was a brief stand-off with local, unarmed people, who did not want the Ukrainian soldiers there. Shots were fired. The reporter said she believed they were warning shots fired into the air.
At 5:42 p.m. Ukrainian time, subscribers to the RIA news agency, which is controlled by the Russian state, received an article stating that four "militiamen" - a term used to describe pro-Russian militants - were dead.
It said they were killed during the storming of the Kramatorsk airfield by Ukrainian forces. It cited as its source an unnamed person in "the people's self-defence force."
A short while after, a correspondent in Kramatorsk went live on the Kremlin-funded Russian-language Rossiya 24 rolling news channel to say between four and 11 of the pro-Russian activists had been killed in the assault. That report triggered a wave of reports in other media, and on social networking sites.
One of the many who circulated the reports of casualties on his Twitter account was Maxim Shevchenko, a member of the Kremlin's human rights council. He said he got the information from speaking to people on the ground.
By about 7:00 p.m. Ukrainian time, RIA news agency was quoting the Russian foreign ministry's human rights representative as saying he was deeply concerned about reports of casualties in eastern Ukraine.
"To all appearances, events are beginning to develop under the worst case scenario," the agency quoted the official, Konstantin Dolgov, as saying.
NO DEATHS - THANK GOD
It was impossible to establish definitively that there were no dead or wounded in the clashes at Kramatorsk airfield. But medical authorities in the city and beyond, contacted by Reuters, said they had no knowledge of any casualties.
Asked if they knew anything about wounded or killed from Kramatorsk, an official with the medical department for the Donetsk region, which includes Kramatorsk, told Reuters: "We do not have any such information."
The deputy mayor of Kramatorsk, Marina Karavan, said when asked the same question on Wednesday: "Not one (injured) person was admitted to any one of the medical establishments of the city, not yesterday, and not today."
Contacted by Reuters on Wednesday, Shevchenko, the member of the Kremlin rights council who Tweeted reports of the casualties, acknowledged they had been wrong.
"I think there are no deaths - thank God," he said.
Circulating incorrect information is not the unique preserve of Kremlin-controlled media. Ukraine's authorities have also made assertions that later turned out to be untrue. All media organisations at times make mistakes.
Countering assertions that Russia was churning out propaganda, Dmitry Peskov, chief spokesman to Russian President Vladimir Putin, turned that allegation back on Western media.
"European TV viewers are currently unable to get information in full," Peskov said on Rossiya television. "These (Russian) arguments don't get through ... because they encounter a concrete wall of censorship."
However, international organisations testify that Russia has a track record of bending the news to suit its political agenda.
In August 2008, Russian troops moved into neighbouring Georgia, on the grounds they were protecting people in the pro-Russian breakaway region of South Ossetia from attack by Georgian security forces.
Around that time, Russia's ambassador to Georgia said in public that Georgian forces had killed about 2,000 civilians in South Ossetia, according to Rossisskaya Gazeta, a state-controlled Russian newspaper.
Later, researchers with New York-based rights group Human Rights Watch gave a death toll of 44, for both civilians and fighters killed in clashes, though they said this was not a comprehensive tally as there could have been deaths their research did not capture.
This week, a report by the United Nations Human Rights office said that accounts of harassment of ethnic Russians in Ukraine during this year's crisis had been "greatly exaggerated." Russia said the report was one-sided.
Maria Lipman, of the Carnegie Moscow Center, a think tank, said Russia was following a pattern.
"The way the events in eastern Ukraine are covered by state television, it is more propaganda than actual coverage."
"Russian officials are talking about Ukraine being on the brink of civil war and since this is the message, they need to support it with evidence - whether or not this evidence exists they are certainly reporting it," Lipman said.
In the Ukrainian capital, an official with Ukraine's SBU security service said it had eavesdropped on conversations among Russian special forces operatives about how heavy casualties could trigger a military intervention by Moscow.
Reuters had no way of independently verifying if the assertion was true.
"Discussions we have documented say that 100-200 people need to be killed and within 90 minutes Russian troop carriers will enter Ukrainian territory," Vitaly Naida, head of the SBU's counter-intelligence department, told a news briefing. (Additional reporting by Lina Kushch in Donetsk, Natalia Zinets in Kiev and Alexei Anishchuk in Moscow; Writing by Christian Lowe; Editing by)