SK Telecom Co., South Korea's top mobile carrier, said Wednesday its first-quarter net profit hiked 65.6 percent from a year earlier, mainly due to the absence of one-off costs.

Net income reached 442.8 billion won ($409.5 million) in the January-March period, compared with 267.3 billion won the previous year, the company said in a regulatory filing.

The figure, however, falls far short of the median consensus of 512 billion won in a poll conducted by Yonhap Infomax, the financial news arm of Yonhap News Agency.

The improved bottom line came as the mobile carrier had logged a relatively big on-year drop in profit a year ago as it had to compensate users in March 2014 for a network failure in which they had trouble making calls and downloading data.

SK Telecom paid the users more than six times the fee they would've been charged during the period.

The company's operating profit jumped 60 percent on-year t 402.7 billion won in the first quarter, also on the back of the absence of one-off costs. But compared with three months earlier, the operating income fell 18 percent as marketing costs increased over the cited months.

Sales rose 0.9 percent to 4.2 trillion won in the same period, as a robust performance from its affiliates including SK Planet Co., its e-commerce platform arm, offset a decline in profit from network subscriptions.

In the conference call, the chief financial officer at SK Telecom said the company is planning a share buyback worth 400 billion won, as part of an effort to boost shareholders' returns.

"We're thinking of about a 400 billion-won worth share buyback over the next year or so... more detailed plans will be carried out after the board meeting," said CFO Lee Yong-hwan.

Shares of SK Telecom ended at 271,500 won on the Seoul bourse on Wednesday, down 3.55 percent from the previous session's close.

The earnings results were released during the trading hours. (Yonhap)