Calls are rising in the United States to ensure fair treatment of Chinese-Americans, observers said, as the US Commission on Civil Rights has sent a letter to the US attorney general about criminal investigations that accused Chinese-Americans of being spies.

The commission, a bipartisan, independent federal agency, argued that the government may be "failing to exercise sufficient due diligence" in criminal investigations accusing Chinese-Americans of espionage.

The agency issued a news release on Monday to reinforce a letter sent on Nov 18 to US Attorney General Loretta Lynch regarding high-profile prosecutions of two Chinese-American scientists.