A man reads a notice in the window of a closed McDonald's restaurant as the company said it halted operations due to a system disruption, in Tokyo on Friday. Reuters

System failures at McDonald's were reported worldwide earlier on Friday, shuttering some restaurants for hours and leading to social media complaints from customers, in what the fast food chain called a "technology outage” that was being fixed.

Chicago-based McDonald's Corp. said the problems were not related to a cybersecurity attack, without giving more details on what caused them.

"We are aware of a technology outage, which impacted our restaurants; the issue is now being resolved," the burger giant said in a statement. "We thank customers for their patience and apologise for any inconvenience this may have caused.”

Earlier, McDonald's in Japan posted on X, formerly Twitter, that "operations are temporarily out at many of our stores nationwide," calling it "a system failure.” In Hong Kong, the chain said on Facebook that a "computer system failure” knocked out orders online and through self-serve kiosks.

China was also affected for several hours, with the outage a hot topic on social media platform Weibo, but the firm later said its online ordering system had been fully restored.

Downdetector, an outage tracker, also reported a spike in problems with the McDonald's app in the last few hours.

Some McDonald’s restaurants were operating normally again after the outage, with people ordering and getting their food at locations in Bangkok, Milan and London.

A worker at a restaurant in Bangkok said the system was down for about an hour, making it impossible to take online or credit card payments but allowing it to still accept cash for orders.

At another location in Thailand’s capital, there was plywood over a door with a sign saying, "Technicians are updating the system," even as customers were ordering again and paying digitally.

A worker at a Milan restaurant noted that the system was offline for a couple of hours and a technician walked them through getting it back up and running.

A spokesperson for McDonald’s in Denmark said the "technology failure” was resolved there and its restaurants were open.

Singapore was also hit, as were Australia and New Zealand according to media reports.