China urged the United States on Friday to thoroughly investigate the suicide of a Chinese postdoctoral researcher following interrogation by US law enforcement authorities, and to stop any discriminatory law enforcement activities targeting Chinese scholars and students.

China is deeply saddened by the tragic incident and has protested to the US, Foreign Ministry spokesman Lin Jian told a daily news conference.

Chinese diplomatic missions in the US swiftly got in touch with the researcher's family and are assisting them in handling relevant matters, Li noted.

Washington should provide a responsible account to the researcher's family and Beijing, and stop imposing wrongful convictions, he said.

For some time, the US has overstretched the concept of national security for political manipulation, and groundlessly interrogated and harassed Chinese scholars and students, he said.

These moves infringe on the legitimate and lawful rights and interests of Chinese citizens, and disrupt the atmosphere of people-to-people exchanges, which cause a grave "chilling effect", Lin said.

China will continue to take necessary measures to firmly safeguard the legitimate rights and interests of its citizens, he said.