The yuan has lost more than 2.5% against the dollar since the festering China-U.S. trade dispute intensified earlier this month. It is now less than a tenth of a yuan away from the 7-per-dollar level authorities have in the past indicated as a floor.
"Short-term fluctuation of the yuan exchange rate is normal, but in the long-run, China's economic fundamentals determine that the yuan will not depreciate persistently," Xiao Yuanqi, the spokesman for the China Banking and Insurance Regulatory Commission (CBIRC), told a finance forum in Beijing.
"Those who speculate and short the yuan will for sure suffer heavy loss."
Xiao was reading from a script prepared for Guo Shuqing, CBIRC's chairman and the Communist Party chief of the People's Bank of China (PBOC). Guo was scheduled to give a speech at the same forum but couldn't make it due to last minute arrangements.
Xiao also said Beijing must look out for hot money moving in and out of the country, as well as large amounts of capital flowing into the frothy real estate market.
"We must be especially vigilant about money from overseas moving in and out in large quantities, and hot speculative money, and we must resolutely fight bubbles in real estate and financial assets," he said.
Chinese policymakers have struggled to manage bubble risks in the property market, the world's largest, without hurting growth in the sector, which is crucial for the wider economy.
(Reporting by Cheng Leng and Ryan Woo; Writing by Yawen Chen; Editing by Sam Holmes)