Recasts paragraph 1 with shares, adds background and details about results in paragraph 2

By Supantha Mukherjee

STOCKHOLM, May 14 (Reuters) - Klarna KLAR.N, the Swedish "buy now, pay later" services provider and online bank, posted first-quarter operating profit and revenue ahead of analysts' expectations on Thursday, sending its shares up over 12% in U.S. premarket trading.

BNPL service providers such as Klarna are benefiting from rising demand for their short-term loans, which allow shoppers to split purchases into installments. The firm's active consumers jumped 21% to 119 million in the quarter.

Klarna focused on profit ahead of growth in the quarter after prioritizing growth over the bottom line in the fourth quarter, an approach which wiped a quarter off its market value.

"It obviously became clear to us that it was important to all the shareholders that they were supportive about the growth, but they also wanted to see the bottom line growing well," Klarna CEO Sebastian Siemiatkowski told Reuters.

But while its quarterly revenue rose 44% to $1 billion, beating estimates of $945 million, Klarna's current-quarter revenue forecast of $960 million to $1 billion was below expectations of $1.07 billion in an LSEG poll of analysts.

Klarna said its quarterly operating income was $17 million compared with a loss of $90 million in the year-earlier period, ahead of expectations of $9 million. Adjusted operating profit rose to $68 million from $3 million a year ago, it said.

Its gross merchandise volume (GMV), a metric for measuring sales, rose 33% to $33.7 billion in the quarter. In the second quarter, Klarna expects GMV of between $35.5 billion and $36.5 billion, versus expectations of $38.1 billion.