SINGAPORE - Asia's largest oil and gas producer PetroChina is buying Keppel Corp's 45.5 percent stake in Singapore Petroleum Company (SPC) for S$1.47 billion ($1.02 billion) and plans to make a general offer to buy the rest of the firm.

SPC's main asset is a refinery in Singapore, Asia's oil trading and pricing hub, and so the acquisition may give PetroChina more leverage and flexibility in oil trading.

It is the first overseas acquisition of a public company by PetroChina, and the move for downstream fuel production adds to efforts by Chinese oil majors to buy upstream oil exploration assets around the world to secure energy supplies.

SPC will become a new platform for the implementation of our international strategy and will provide a broader foundation and stable path for development, PetroChina said in a statement.

The deal valued the Singapore oil refiner at S$3.2 billion or a 24 percent premium to its market value of S$2.6 billion according to Reuters data. It was an equivalent of S$6.25 for each SPC share, compared to Friday's closing price of S$5.04.

The deal still needs regulatory approval, including from the Chinese government. Under Singapore rules, since PetroChina is buying more than 30 percent of the company it would need to make an offer for the rest.

Keppel, the world's largest offshore oil rig builder, said in the statement that together with PetroChina it plans to explore opportunities in the offshore oil industry and in other areas.

The divestment of our stake in SPC would enable Keppel to seize opportunities, Keppel's chief executive officer Choo Chiau Beng said.

SPC shares a 285,000 barrels per day refinery in Singapore with U.S. energy major Chevron Corp, and it also owns upstream oil and gas exploration and production concessions in Australia, Southeast Asia and China.

The refinery's oil products are sold at home and exported to Southeast Asia and China.

The announcement came after PetroChina said earlier this month that it plans to raise up to 100 billion yuan ($14.66 billion) in debt to finance key strategic projects this year.

PetroChina said Deutsche Bank is acting as sole financial advisor for PetroChina.

Deutsche Bank said the deal valued SPC at 17.2 times its 2009 forecast earnings, based on consensus estimates of 36.3 Singapore cents per share.

SPC shares have risen by 122 percent so far this year, outpacing a 27.5 percent rise in the broader Singapore Straits Times Index .FTSTI.

($1=1.442 Singapore Dollar)

($1=6.822 Yuan)

(Additional reporting by Saeed Azhar in SINGAPORE, Michael Flaherty and Joseph Chaney in HONG KONG, editing by Neil Chatterjee)