MANILA, May 13 (Reuters) -

Gold miner OceanaGold Philippines Inc's shares fell as much as 6% below their initial public offering (IPO) price in the first 15 minutes of trading on their market debut on Monday.

The shares opened at 13.34 pesos ($0.2314) a touch above their IPO price of 13.33 pesos, but subsequently lost ground.

Toronto-listed miner OceanaGold Corp sold 20% in subsidiary OceanaGold Philippines via an 6.078 billion pesos IPO, the first listing in the Southeast Asian nation this year and the country's first public debut for a mining firm since 2012.

The gold and copper miner conducted its IPO to comply with a regulatory requirement for its operations in northern Philippines.

OceanaGold's Didipio mine started commercial operations in 2013 and has a mine life of up to 2035. ($1 = 57.64 Philippine pesos) (Reporting by Neil Jerome Morales; Editing by John Mair)