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 has ruled.

Administrative Law Judge Geoffrey Carter said in a ruling posted on the board's website on Thursday that Wal-Mart violated labor laws by "disciplining or discharging several associates because they were absent from work while on strike".

Most of the allegations in the ruling related to a coordinated set of strikes at various Wal-Mart stores in May and June of 2013, the ruling said. Carter was ruling on a complaint filed by the NLRB on behalf of a union-backed worker group, OUR Walmart, in 2014.

Wal-Mart said it disagreed with the ruling, which it can appeal to the labor agency's board in Washington.

"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 ordered that Wal-Mart must 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.

The decision comes one day after Wal-Mart announced that it would raise pay for 1.2 million employees -- nearly its entire U.S. workforce -- in 2016 as part of a previously announced $2.7 billion investment in wages and training.

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

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