Earlier in the day, US media reported, citing sources, that Chinese-linked hackers allegedly accessed the email account of Burns, compromising hundreds of thousands of government emails.
"China firmly opposes and combats cyber attacks and cyber theft in all forms," Liu said in a statement on Thursday.
"This position is consistent and clear. Given the virtual nature of cyberspace and the fact that there are all kinds of online actors who are difficult to trace, identifying the source of cyber attacks is a complex technical issue."
Liu further highlighted the importance of having enough evidence when identifying cyber-related incidents, rather than make groundless speculations and allegations.