(Adds details on Wal-Mart's stance, background)

By Nathan Layne

Jan 21 (Reuters) - Wal-Mart Stores Inc unlawfully retaliated against workers who participated in strikes in 2013 and must offer to reinstate 16 dismissed employees, a National Labor Relations Board judge ruled on Thursday.

Administrative Law Judge Geoffrey Carter said in a ruling posted on the board's website that the U.S. retailer violated labor law by "disciplining or discharging several associates because they were absent from work while on strike".

The ruling was hailed by one labor group as a "huge victory" for employees, although Wal-Mart indicated it would likely appeal the decision to the labor agency's board in Washington, and pointed to its recent efforts to improve worker benefits and raise pay.

"We disagree with the Administrative Law Judge's recommended findings and we will pursue all of our options to defend the company because we believe our actions were legal and justified," Wal-Mart spokesman Kory Lundberg said.

Carter was ruling on a complaint filed by the NLRB on behalf of a union-backed worker group, OUR Walmart, in 2014. Most of the allegations related to a coordinated set of strikes collectively referred to the "Ride for Respect" because they involved traveling by bus to the company's headquarters in Arkansas for protests at its shareholders' meeting in June 2013.

Wal-Mart had argued that it was lawful to discipline workers with unexcused absences to participate in the protests because the strikes constituted "intermittent work stoppages" not protected under labor law.

But the judge found the "Ride for Respect" differed materially from other previous work stoppages not protected by law because, among other factors, it was not a brief strike -- meaning the risk for workers was higher -- and because it was not scheduled close in time with other strikes.

Carter ordered Wal-Mart to offer 16 former workers their previous jobs and make them "whole for any loss of earnings and other benefits suffered as a result of the discrimination against them".

Wal-Mart was also ordered to hold a meeting in more than two dozen stores to inform workers of their rights to organize under U.S. labor law.

Jessica Levin, spokeswoman for labor group Making Change at Walmart, which is backed by the United Food & Commercial Workers International Union (UFCW), described the ruling as a "huge victory" for the dismissed workers as well as "Walmart workers everywhere".

It was unclear what impact, if any, the decision would have on the efforts by Making Change at Walmart and other groups to pressure Wal-Mart on wages and benefits. The UFCW has tried for years to organize Wal-Mart workers and the hurdles remain high.

The ruling comes a day after Wal-Mart announced that it was raising wages for 1.2 million U.S. workers in 2016 as part of a $2.7 billion investment over two years in wages and training.

While denting profits near term, Wal-Mart has said the investments are helping improve customer service and worker engagement scores.

(Reporting by Nathan Layne in Chicago; Editing by Sandra Maler)