HONG KONG, June 19 (Reuters) - China’s central bank urged investors on Tuesday to remain calm as the world’s second-largest economy has growing capabilities to cope with external shocks, after Chinese stock markets tumbled on escalating trade friction with the United States.

“There are ups and downs in the stock market and so, investors should be calm and rational,” Yi Gang, governor of the People’s Bank of China, said on the central bank’s website www.pbc.gov.cn.

“China is in good position to cope with all kinds of trade frictions,” Yi said.

Earlier in the day, Shanghai stocks lost nearly 4 percent to a two-year low as U.S. President Donald Trump’s fresh tariff threats against China raised the spectre of a full-blown trade war. (Reporting by Lee Chyen Yee in Singapore and Meg Shen in Hong Kong)