Zynga Inc. said on Monday it is cutting 520 jobs,

Zynga Inc. said on Monday it is cutting 520 jobs, or 18% of its staff, in a move that the social-gaming site’s founder described as “necessary to move forward.”

In a memo to employees, Mark Pincus said the “impact of these layoffs will be felt across every group in the company.”

“Today is a hard day for Zynga and an emotional one for every employee of our company,” he wrote. “None of us ever expected to face a day like today, especially when so much of our culture has been about growth.”

Zynga said the cuts are expected to result in annualized cost savings of $70 million to $80 million.

In his memo, Pincus said the reductions were part of Zynga’s strategy to become more competitive in the gaming market, particularly in the mobile arena.

“Mobile and touch screens are revolutionizing gaming,” he said. “Our opportunity is to make mobile gaming truly social by offering people new, fun ways to meet, play and connect. By reducing our cost structure today, we will offer our teams the runway they need to take risks and develop these breakthrough new social experiences.”

But the cuts will likely also be viewed as yet another sign that Zynga continues to struggle in the social-media market where it emerged as an important player as Facebook Inc.’s FB -2.05% social-gaming partner.

The company, which is best known for such games as “FarmVille” and “CityVille,” has struggled to bounce back as revenue from older games slowed.

Zynga in late April gave a disappointing outlook , which sent its stock falling. The shares have dropped nearly 13% in the last three months.