(Reuters) - The New York Times Co's NYT.N adjusted operating profit fell 13 percent in the first quarter as ad sales declined in its print and digital businesses and costs rose.

The sun peaks over the New York Times Building in New York August 14, 2013. REUTERS/Brendan McDermid

Shares of the publisher, which is spending heavily to strengthen its advertising technology, fell 4.4 percent to $12.32 in afternoon trading on Tuesday.

The Times, like many other newspaper and magazine publishers, has been struggling with a steady decline in print ad revenue for the past couple of years.

To make up for sliding print ad sales, the company has been pushing into digital offerings with investments in technology and initiatives such as distributing Google Cardboard virtual reality headsets to subscribers.

The Times plans to invest more than $50 million over the next three years to strengthen its digital presence outside the United States.

Its adjusted operating costs rose 1 percent in the first quarter. Print ad revenue declined 9 percent, the seventh straight quarter of fall.

Digital ad revenue, which accounts for about a third of total ad revenue, fell 1.3 percent.

Chief Executive Mark Thompson said in February that 2016 would be “an investment year,” in which operating profit would be under pressure due to spending on its digital business.

The Times said on Tuesday that it expected adjusted operating costs to increase in low single-digit percent in the second quarter as it ramps up investments.

Circulation revenue from the company’s digital-only subscriptions rose 14.2 percent in the first quarter.

Combined digital-only subscriptions totaled about 1.4 million at the end of the quarter, a net increase of 87,000 from the preceding quarter.

The company expects combined digital-only subscriptions to exceed 1.5 million by the end of the year, Thompson said on a post-earnings conference call.

The Times’ adjusted operating profit fell to $51.5 million from $59.2 million.

The net loss attributable to shareholders narrowed to $8.3 million, or 5 cents per share, from $14.3 million, or 9 cents per share, a year earlier.

Excluding items, the company earned 10 cents per share.

Total revenue fell 1.2 percent to $379.5 million.

Analysts on average had expected a profit of 8 cents and revenue of $377.3 million, according to Thomson Reuters I/B/E/S.