BEIJING - A senior commerce official said Friday that so far, 490 out of the world top 500 companies have invested in China and established more than 1,600 R&D centers and regional headquarters.

Transnational corporations have kept investing more in China since the country adopted the policy of opening up to the outside world in the late 1970s. The companies have been playing an increasingly important role in boosting the nation's economic development, Gao Hucheng, a vice commerce minister, said at a meeting.

Foreign-invested firms have reaped great benefits from this huge market. Sales of these companies exceeded 33 trillion yuan ($5.24 trillion) in China in 2010 alone, Gao said, adding that the nation has become a safe haven and a main source of income for many foreign-invested firms during the international financial crisis.

Meanwhile, China has stepped up its investment in other parts of the world. By the end of 2011, China's outbound direct investment topped $380 billion.

There were more than 18,000 Chinese-funded companies operating in 178 countries and regions at the end of last year, with total assets reaching approximately $1.6 trillion, Gao said.