Community Health Systems, a major US hospital operator, said Monday that hackers likely from China broke into its systems and stole identification data for some 4.5 million patients.

Community Health said the hackers infiltrated its systems in April and June this year, using "highly sophisticated malware and technology" to bypass its data security protection.

The company said that, working with computer security experts, it discovered information to conclude that the attackers were a group originating from China which works steadily to gain access to a target's systems in order to steal data rather than cause damage to the systems.

Operator of 206 hospitals across the country, Community Health said in a securities filing that the hackers took data on patients' names, addresses, birthdates, phone numbers and Social Security numbers. But it said they did not obtain medical information on patients or any credit card data.

It said it would offer patients affected by the breach identity theft-protection services.