(Reuters) -Singapore Telecommunications posted a 64% drop in full-year net profit on Thursday hit by a S$3.1 billion ($2.30 billion) impairment charge, majority of which relates to its mobile network operation unit Optus. Australia's second-largest telecom company Optus has been marred by multiple setbacks, including a massive network-wide outage in the country, data breaches and steep declines in fixed carriage revenue amid increased capital costs.

The non-cash charge comprises a S$2 billion provision on the goodwill of Optus, while S$470 million relates to Optus' enterprise fixed access network assets.

Excluding the one-time charge, company's underlying net profit rose 10% to S$2.26 billion, underpinned by higher contributions from regional associates including Airtel and Advanced Info Service.

Southeast Asia's largest telecom firm said net profit for fiscal year 2023 was S$795 million, compared with S$2.23 billion a year ago.

Revenues from Optus, the company's top revenue generator, was largely unchanged at A$8.06 billion ($5.34 billion).

SingTel proposed a final dividend of 9.8 Singapore cents per share, compared with 5.3 Singapore cents a year earlier.

($1 = 1.5103 Australian dollars)