(Adds details, share price)
* Q3 profit 5.1 bln pesos vs 1.1 bln pesos year ago
* Net profit up for 3rd straight quarter
* Nine-month profit rises 61 pct to 19.2 bln pesos
MANILA, Nov 14 (Reuters) - San Miguel Corp, the Philippines' most diversified conglomerate, increased its third-quarter profit by more than four-fold compared with a year ago after aggressively expanding into sectors such as oil refining and power generation.
Net profit rose to 5.1 billion pesos ($124 million) in July-September from 1.1 billion pesos a year earlier, according to Reuters calculations based on nine-month earnings announced by San Miguel on Wednesday. No estimates were available as analysts in the Philippines do not make quarterly forecasts.
San Miguel posted its third consecutive quarterly profit growth after diversifying into sectors including mining, telecommunications and infrastructure over the past four years to accelerate earnings growth.
But shares in the group have lagged the benchmark this year, with some investors unconvinced that its recent acquisitions would be a good fit in the long term. The stock has dropped more than 6 percent compared with the 25 percent gain in the main stock index.
"Given the numerous acquisitions, the changes in the business model, most investors are still thinking whether it's the right time to buy San Miguel," said Gregg Ilag, an analyst at AB Capital Securities Inc in Manila. "Valuations also follow the changes in the business model. You can't really value something that's constantly changing right now."
The stock ended unchanged on Wednesday, before the earnings announcement.
In March, San Miguel's unit Petron Corp, the country's largest oil refiner, completed a $610 million acquisition of 65 percent of Esso Malaysia Bhd, 100 percent of ExxonMobil Malaysia Sdn Bhd, and 100 percent of ExxonMobil Borneo Sdn Bhd, boosting its oil refining capacity and giving it control of 560 retail stations.
In the following month, San Miguel bought stakes in Philippines Airlines and a sister carrier Air Philippines Corp from Filipino billionaire and brewing rival Lucio Tan in a deal worth about $500 million.
Last month, San Miguel's President Ramon Ang said the group was looking to invest in a private Asian company with a market value of at least $5 billion. San Miguel did not identify the firm due to confidentiality obligations.
On Wednesday, San Miguel said it was in talks for possible investments in Cayman Airways and in Cayman Islands.
Net income rose 61 percent to 19.2 billion pesos in January-September from a year earlier, backed by strong sales in oil refiner Petron, and the group's power and food subsidiaries.
Operating profit at its SMC Global Power unit jumped 26 percent to 13.9 billion pesos.
The group's flagship San Miguel Brewery Inc, the country's second-most valuable firm, expanded its operating profit by 5 percent to 15.4 billion pesos.
San Miguel Pure Foods Co Inc, which launched a secondary offer of up to 7.5 billion pesos worth of shares, posted flat net profit in the nine-month period.
($1 = 41.1 pesos) (Reporting by Erik dela Cruz; Editing by Ryan Woo and Rosemarie Francisco)