UPDATE 1-Hynix posts Q4 loss; raises investment by 20 pct

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* Q4 operating loss 167 bln won vs 174 bln won loss fcast

* Plans 4.2 trln won in 2012 capital spending, up 20 pct y/y

SEOUL, Feb 2 (Reuters) - Hynix Semiconductor Inc , the world's No.2 computer memory chip maker, reported its second consecutive quarterly loss, hit by tumbling computer chip prices as consumers ditched desktops and notebook PCs in favour of tablets and smartphones.

The South Korean firm warned that global PC market growth would remain subdued due to a fragile economy in the first half of this year and may start to rebound in the second half, led by new products such as ultrabooks.

Hynix, which competes with sector leader Samsung Electronics and Japan's Toshiba Corp, posted an operating loss of 167 billion won ($148 million) for the three months ended December, compared with an average forecast of a 174 billion won loss by Thomson Reuters I/B/E/S.

That compared with a profit of 294 billion won a year ago and loss of 277 billion won in the preceding quarter.

Hynix shares rose 18 percent over the past three months, outpacing the broader market, which gained 2 percent.

Hynix, which counts South Korea's top mobile carrier SK Telecom as its biggest shareholder after a $3 billion deal last year, said it would raise capital spending by 20 percent this year to 4.2 trillion won and use more than half of the investment to boost production of mobile and flash memory chips.

Its bigger rival Samsung warned last week that computer memory chips will continue to remain oversupplied in the first quarter due to weak demand.

Hynix said average selling prices of dynamic random access memory (DRAM) chips fell 19 percent in the fourth quarter from the previous quarter, while prices of flash chips fell 17 percent. ($1 = 1126.4000 Korean won) (Reporting by Miyoung Kim; Editing by Jonathan Hopfner)