Gap, the clothing retailer reported another quarter of declining sales recently, a sign of deepening trouble in its battle to keep up with fast fashion and online retailers.

The 47-year old apparel maker Gap, known for its trademark blue denim, khakis and other mostly youth-oriented looks, saw sales fall at all three its store brands: Gap, Banana Republic and Old Navy.

In the first quarter, sales fell 6.0 percent to $3.44 billion, with Banana Republic sinking the most at 11 percent. Old Navy, the group's cheapest line mostly aimed at children and teens, outperformed its sister chains for most of 2015.

Key challenges for all three though include toughened competition from H&M, Uniqlo and other fast fashion chains, as well as the headwinds from a broader tilt against brick-and-mortar stores as more shoppers go online.

A year ago Gap announced plans to cut 175 namesake stores in North America, pledged renewed focus to streamline its operations and whittle its presence internationally to the most promising markets.

According to chief executive Art Peck, the industry is evolving and they should transform at a faster pace, while focusing their energy on what matters most to their customers.Peck said more details would be revealed when the company reports earnings on May 19.