Eye test records and personal contact details of hundreds of military personnel including soldiers posted overseas were sent to China in a significant data security breach, Fairfax Media has learnt.

The records, which included in many cases mobile phone numbers of personnel, were sent to a processing facility in China's Guangdong province by a health contractor, Luxottica Retail Australia.

The personnel affected are understood to have included soldiers posted overseas to Afghanistan and special forces commandos who went on to be deployed to Iraq.

Luxottica had its contract terminated last year, a fact both Defence and its principal healthcare contractor, Medibank Health Solutions, announced in statements, admitting that records had been sent offshore. However, neither of those statements acknowledged that China was a destination for the data.

The revelations raised particular concern within the Defence establishment because of China's extensive involvement in state-sponsored hacking and cyber-espionage, with Beijing showing a particular interest in accessing personal records of government workers in the US.

Furious Defence Department officials demanded a "please explain" from Medibank Health Solutions, the principal contractor that handles healthcare referrals for Defence personnel.

MHS took immediate steps to cancel Luxottica's contract. It is understood Luxottica sent records to other countries as well, but China is the country of particular concern. Under the subcontracts between MHS and health providers, records must be kept within Australia.

Concern has skyrocketed over Beijing's use of hacking recently. At the weekend, US presidential hopeful Hillary Clinton accused China of "trying to hack into everything that doesn't move in America".

Washington officials have blamed China for a massive data breach of the US Office of Personnel Management, which could have compromised the records of about 4 million government employees. Beijing has denied the accusations.

A spokesman for MHS said on Tuesday: "Following the comprehensive review of this issue undertaken by Luxottica at the request of Medibank Health Solutions, Luxottica confirmed it was confident that the integrity of ADF personnel data had not been compromised."

Luxottica owns subsidiary Tristar Optical, which has facilities in the city of Dongguan in Guangdong.

In its original statement last year, MHS said that it had "detected this breach as part of its regular review process … and immediately raised concerns with Luxottica".

Defence said in its statement from last year that it took the issue "very seriously". It said MHS had promised that no other subcontractor had sent records offshore.

MHS began providing services referring Defence personnel to subcontractors for healthcare in late 2012.

Luxottica has been contacted for comment.

Follow us on Twitter