SINGAPORE — Singapore Telecommunications Ltd (Singtel), the parent of Australian telecoms provider Optus, said on Thursday its planned software update was not the root cause for an outage last week, contradicting Optus' claims earlier this week.

More than 10 million Australians were hit by the 12-hour network blackout at the Singtel-owned telecom firm on Nov 8, frustrating customers and raising wider concerns about its telecommunication infrastructure.

Optus had earlier in the week said an initial investigation found the company's network was affected by "changes to routing information from an international peering network" after a "routine software upgrade".

Singtel, while confirming that Singtel Internet Exchange (STiX) is one of Optus' international networks that connects to the global internet, denied that the routine software upgrade was the root cause.

"We are aware that Optus experienced a network outage after the upgrade when a significant increase in addresses being propagated through their network triggered preset failsafes," Singtel said.

Singtel's statement comes a day before Optus chief executive officer Kelly Bayer Rosmarin faces an Australian senate inquiry into the massive outage. REUTERS