BEIJING (AFP)--China's top oil producer has issued the nation's first medium-term U.S. dollar notes, the central bank said Thursday, in yet another sign Beijing is keen to facilitate companies' overseas expansion.

China National Petroleum Corp.'s issue marks a "milestone" because it "offers a new forex financing channel for companies," the People's Bank of China Ltd. (601988.SH) said in a statement.

In a separate statement, the China National Petroleum Corp., parent of Hong Kong-listed Petrochina Co. (PTR), said it had raised $1 billion in the issue of three-year, floating-rate notes.

"It provides a driver for competent firms to go abroad and strongly supports their overseas business expansion," the central bank statement said.

China is increasingly keen on buying overseas mining assets and other resources through state-owned companies, taking advantage of low prices on the international market due to the global financial crisis.

In a recent high-profile example of Chinese corporate ambitions abroad, aluminium producer Chinalco has proposed to invest $19.5 billion in Australian mining giant Rio Tinto PLC (RTP).

The deal is still under review by the Australian government and would mark China's largest ever foreign investment if approved.