China's state media, including Global Times and a social media account run by CCTV, claimed the attack was "government-backed" and came from the United States.
The U.S. embassy in Beijing didn't immediately reply to a Reuters' request for comments.
The Wuhan Municipal Emergency Management Bureau said in a statement that some network equipment at the Wuhan Earthquake Monitoring Center was under a cyberattack by an overseas organisation, but didn't specify the time of the attack.
A backdoor program, capable of controlling and stealing seismic activity data, was inserted in the equipment, according to China Daily.
China's foreign ministry condemned the attack, saying the "irresponsible" act has threatened China's national security.
"China will take necessary measures to safeguard its cyber security," spokesperson Mao Ning said at the ministry's regular press conference.
Microsoft earlier this month said Chinese hackers had breached senior U.S. officials' emails, a claim which Beijing refuted, calling it "disinformation."
(Reporting by Ethan Wang and Ryan Woo; Editing by Bernadette Baum)
