A Canadian company that owns many popular restaurant chains says it was hit with a "malware outbreak" on Friday, causing a "partial network outage" at some locations.

Recipe Unlimited — formerly Cara Operations — said certain restaurants under the brands Swiss Chalet, Harvey's, Milestones, Kelseys, Montana's, Bier Markt, East Side Mario's, The Landing Group of Restaurants and Prime Pubs brands have been affected.

As a result, some locations have temporarily closed while others are offering reduced services such as no debit and credit card transactions unless they can be done manually.

Malware is malicious software created to damage or disable a computer system. Recipe Unlimited declined to offer further details about the attack on its computer system or specific numbers of restaurants affected.

Hello! Unfortunately we are encountering issues and are looking into resolving them as soon as possible. Thanks for reaching out to us! —@SwissChaletCA

The company said in response to the incident, it took a number of its systems offline and suspended internet access at affected locations "as a precaution."

"Our priority is to continue working diligently with third-party security experts and internal teams to resolve the situation as quickly and effectively as possible," said Recipe Unlimited in a statement.

The problem sparked many customer complaints on social media. Lando Fiore posted a photo on East Side Mario's Facebook site showing a sign, displayed at one of its restaurants in Newmarket, Ont. It stated that the restaurant was closed for the day because "the head office computer was hacked."

Fiore told CBC News that he and a friend drove to an East Side Mario's location in Aurora, Ont., on Sunday and discovered it was closed. They thought it was an isolated incident and decided to dine instead at the Newmarket location.

"We were just appalled," said Fiore, upon discovering that the Newmarket location was also closed. "It can't be good for business."

On Sunday, Lando Fiore posted a photo on Facebook showing this sign displayed at an East Side Mario's restaurant in Newmarket, Ont. It stated that the restaurant was closed because "the head office computer was hacked." (Lando Fiore/Facebook)

Over the the weekend, many people also complained on Swiss Chalet's Facebook site about slow service and difficulty ordering online. The chain repeatedly replied that "due to unforeseen circumstances, we are currently experiencing a system outage." It added that its "teams are working diligently to have this corrected."

Recipe Unlimited franchises and/or operates more than 1,000 restaurants, mainly in Canada.