Wall Street Journal-owner News Corp has reported a surprise quarterly profit, driven by strong growth in earnings at its book publishing and subscription video services units. 

Trying to offset declines in print advertising, News Corp has been focusing on its book publishing business, which includes the famous HarperCollins brand, and its digital businesses. 

"News Corp reaped rewards from our digital strategy this quarter, underscored by a robust rise in digital subscriptions across our media properties, a sharp increase in digital audio book sales," chief executive Robert Thomson said. 

The company, controlled by media mogul Rupert Murdoch, said HarperCollins' core earnings rose 29% in the quarter, helped by strong sales of audio books and new releases such as "Fing" by David Walliams.

Revenue from book publishing rose about 6% to $421m, and the segment's earnings before interest, tax, amortization and depreciation jumped 29% to $53m.

Analysts' were expecting revenue of $414m from the unit, according to IBES data from Refinitiv. 

The New Foxtel, part of subscription video services division, reported an 80% rise in paying subscribers to 714,000, since the beginning of 2019, News Corp said. 

Net income available to stockholders was $10m, or two cents per share, in the three months ended March 31, compared with a loss of $1.13 billion, or $1.94 per share, a year earlier. 

Excluding one-time items, the company reported a profit of four cents per share, while analysts on average expected it to breakeven on a slight net loss. 

The company said revenue rose to $2.46 billion from $2.09 billion.