* Gunman appeared to have combat experience
* Thought to have travelled to central city of Konya
* Selfie video shows alleged assailant in Istanbul
* Report suggests may be of Kyrgyz origin
By Humeyra Pamuk and Daren Butler
ISTANBUL, Jan 3 (Reuters) - The gunman who killed 39 people in an Istanbul nightclub on New Year's Day in an attack claimed by Islamic State appears to have been well versed in guerrilla warfare and may have trained in Syria, a newspaper report and a security source said on Tuesday.
The attacker, who remains at large, shot dead a police officer and a civilian at the entrance to the exclusive Reina nightclub on Sunday. He then opened fire with an automatic rifle inside, reloading his weapon half a dozen times and shooting the wounded as they lay on the ground.
In a statement claiming the attack on Monday, Islamic State described the club as a gathering point for Christians celebrating their "apostate holiday" and said the shooting was revenge for Turkish military involvement in Syria.
"The assailant has experience in combat for sure ... he could have been fighting in Syria for years," one security source told Reuters, saying that he was likely to have been directed in his actions by the jihadist group.
The Haberturk newspaper said police investigations had revealed that the gunman had entered Turkey from Syria and went to the central city of Konya in November, travelling with his wife and two children so as not to attract attention.
CNN Turk said he was believed to be of Kyrgyz origin.
Turkish officials have not commented on the details of the investigation. But government spokesman Numan Kurtulmus said on Monday that the authorities were close to fully identifying the gunman, after gathering fingerprints and information on his appearance, and had detained eight other people.
A selfie video of the alleged attacker, apparently walking around Istanbul's central Taksim Square, was broadcast by Turkish news channels on Tuesday as police operations to try to track him down continued.
Kurtulmus made no reference to the Islamic State claim of responsibility on Monday but said it was clear Turkey's military operations in Syria had annoyed terrorist groups and those behind them.
NATO member Turkey is part of the U.S.-led coalition against Islamic State and since August has been conducting military operations inside Syria to drive the radical Sunni militants, as well as Kurdish militia fighters, away from its borders.
Islamic State has been blamed for at least half a dozen attacks on civilian targets in Turkey over the past 18 months; but, other than assassinations, it was the first time it has directly claimed any of them. It made the statement on one of its Telegram channels, a method used after attacks elsewhere.
Haberturk cited a barman at the club as saying the gunman had thrown explosive devices several times during the shooting spree, apparently in order to disorientate people and give himself time to reload.
Several witnesses who spoke to Reuters also said there had been small explosions during the attack. (Writing by Nick Tattersall; Editing by Mark Trevelyan)