* Video purports to show separatist commander Ivan Strelkov
* Kiev alleges he is Russian agent provocateur
* He says some of his men saw action in Syria
* Denies receiving support from Russia
By Christian Lowe and Pavel Polityuk
KIEV, April 26 (Reuters) - For weeks, Ukraine's intelligence services have been tracking a mysterious man with a pencil moustache who, they say, is Russia's chief agent provocateur tasked with stirring up armed revolt in Ukraine.
The closest anyone had come to spotting him was a crude artist's impression issued by Ukraine's State Security Service. On Saturday, he - or at least someone answering to his name - came out of the shadows.
A Russian newspaper posted online video of what it said was an interview with Igor Ivanovich Strelkov, the man Kiev and Western intelligence agencies say is the Russian covert operative leading a unit of pro-Moscow insurgents in the eastern city of Slaviansk.
In the interview, the man, with what looked like the same moustache and features as the person in the drawing, denied Russia was involved in the insurgency. In fact, he complained that Russia had "not given us a single gun, or a single bullet."
But the account he gave - if he is indeed a leader of the armed rebellion in Slaviansk - is one of the first detailed descriptions of who the insurgents are, how they operate and what they hope to achieve.
His unit had been formed in Crimea, the Ukrainian region annexed by Moscow earlier this year, he said in the interview with the Komsomolskaya Pravda newspaper.
About two-thirds were Ukrainian citizens, he said, without explaining the origins of the rest. He did not say anything about his own nationality.
"A large part of the people have combat experience," he said. "Many fought in the ranks of the Russian armed forces, including Ukrainian citizens, they fought in central Asia. There are people with experience of combat in Iraq and Yugoslavia as part of the Ukrainian armed forces."
He said some of them had been in Syria, though he gave no details on what they were doing there or on which side of the Syrian conflict they had been. Moscow is a close ally of Syrian President Bashar al-Assad.
Once in Slaviansk, the core of his unit had been joined by local volunteers, he said.
The man in the video was sitting at a desk in front of wall map of Slaviansk, while on the floor behind him was what appeared to be a mortar tube.
Dressed in clean camouflage fatigues, he spoke softly, calmly and with precision, especially when giving details of military formations and equipment.
He said his men had scavenged weapons from Ukrainian police and army bases they had captured. He said they had more than 100 automatic weapons, several grenade launchers, a large amount of munitions and six armoured vehicles.
He stressed his men did not want to kill their "brothers" in the Ukrainian armed forces, many of whom, he said, had been sent to Slaviansk against their will.
Russia has denied sending troops or undercover agents into eastern Ukraine.
Whether intentionally or not, the man in the video gave an insight into the tensions and divisions within the pro-Russian separatist movement, which has seized about a dozen official buildings around eastern Ukraine.
He said that all the local recruits to his force were opposed to the Western-backed government in Kiev, which they viewed as illegitimate, and were loyal to the self-proclaimed Donetsk People's Republic.
About 80 percent of them, he said, wanted their region to become part of Russia.
"Some of them, perhaps, are not burning with a desire to join the Russian Federation but in any case do not want to be under the authority of those people who seized power in Kiev," he said.
The separatist revolts dotted around eastern Ukraine have been largely disparate.
He said the Slaviansk separatists had agreed to cooperate with the pro-Russian rebels in the regional capital, Donetsk, who say that they represent the leadership of the Donetsk People's Republic.
"We made that agreement to avoid creating a mass of different centres of resistance which are at odds with each other," he said in the video.
"The agreement wasn't easy for us, because in the resistance we have quite a lot of grievances about the leadership of the Donetsk People's Republic, which has been able to do almost nothing since the seizure of the Donetsk governor's office." (Editing by Andrew Roche)