* Teargas fired near Government House, witnesses see three police wounded
* Police operation involves 15,000 officers; 100 protesters arrested
* First of five sites reclaimed from protesters, police say
* "Reforms will benefit your children, too," protest leader tells police (Updates with teargas fired, officers wounded)
By Athit Perawongmetha and Damir Sagolj
BANGKOK, Feb 18 (Reuters) - At least three police officers were wounded as Thai authorities launched an operation to clear anti-government protesters from streets in Bangkok on Tuesday, one with what appeared to be a gunshot wound to the head, Reuters witnesses said.
Three Reuters witnesses said they heard what sounded like gunfire in the Thai capital and saw firearms being carried by both sides. Authorities did not immediately confirm that shots had been fired.
Television pictures showed clouds of teargas and police crouching behind riot shields as officers clashed with protesters near Government House. It was not clear who had fired the teargas and the authorities blamed protesters.
"I can guarantee that teargas was not used by security forces. The forces did not take teargas with them," National Security Council Chief Paradorn Pattanathabutr told Reuters.
"We understand protesters are the ones who threw teargas at the security forces. Police are armed with just batons and shields and no rubber bullets are being used."
The protesters have been rallying since November to try to oust Prime Minister Yingluck Shinawatra, whom they view as a proxy for her elder brother, Thaksin Shinawatra, a former premier and telecoms tycoon toppled in a military coup in 2006.
Security officials said 15,000 officers were involved in an operation, called the "Peace for Bangkok Mission", to reclaim protest sites around government offices in the centre and north of the capital.
The Erawan Medical Center, which monitors Bangkok hospitals, said 14 people were hurt in the clashes with no reports of any deaths.
Live television pictures showed police with shields and batons pushing and jostling with protesters near Government House. One man could be seen bleeding from a head wound.
Police said about 100 protesters had been arrested in an early morning operation to clear demonstrators from a protest site near the Energy Ministry.
The protests are the latest instalment of an eight-year political battle broadly pitting the Bangkok middle class and royalist establishment against the poorer, mostly rural supporters of Yingluck and her billionaire brother Thaksin.
Demonstrators accuse Thaksin of nepotism and corruption and say he used taxpayers' money for populist subsidies and easy loans that have bought him the loyalty of millions in the populous north and northeast.
Yingluck has been forced to abandon her offices in Government House by the protesters, who have also blocked major intersections since mid-January.
Bluesky TV, the protest movement's television channel, had earlier shown protest leader Suthep Thaugsuban addressing police lines near Government House.
"We are not fighting to get power for ourselves," Suthep said. "The reforms we will set in motion will benefit your children and grandchildren, too. The only enemy of the people is the Thaksin regime."
Labour Minister Chalerm Yoobamrung, who is in charge of the security operation, has said police would reclaim sites near Government House, the Interior Ministry and a government administration complex in north Bangkok as well as the Energy Ministry.
The largest protest sites in the city's business and shopping districts are not included for now. (Addtional reporting by Apornrath Phoonphongphiphat, Amy Sawitta Lefevre, Prapan Chankaew and Panarat Thepgumpanat; Writing by Alex Richardson; Editing by Alan Raybould and Robert Birsel)