Singaporean telco Singtel has denied reports its interested in selling a significant stake in its Australian unit Optus to private equity firm Brookfield.

Reuters said today that Singtel is in advanced talks with Canada's Brookfield over the sale, that would value Optus at around AU$18 billion ($11.9bn).

But in a stock exchange filing Singtel said: "There is no impending deal to offload Optus for the said sum, as reported.

"That said, we regularly conduct strategic reviews of our portfolio to optimize the value of our assets and businesses and will explore all options to maximize shareholder value."

Optus serves more than 10 million customers in Australia and is the country's second-biggest operator. Singtel has owned the operator since 2001.

But in November the telco was hit by a severe outage which lasted around 16 hours, and eventually led to the resignation of CEO Kelly Bayer and Optus' head of networks, Lambo Kanagaratnam, who stepped down last week.

Earlier this month Singtel sold a 0.8 percent stake in Indian telco Bharti Airtel for S$950 million ($710m) to US-based investment firm GQG Partners. The company said it will use the funds to invest in data centers and IT services.

"Optus remains an integral and strategic part of the Singtel and we are committed to Australia for the long term. Our current focus has been on improving network resilience and conducting a CEO search," added Singtel in its announcement.