"We are not afraid to do what's necessary to make sure that Microsoft meets us at the bargaining table over key issues like remote work options and outsourcing," ZeniMax Workers United said on X, formerly Twitter.

"Today, we are on strike."

The group, part of the Communication Workers of America (CWA), said that hundreds of ZeniMax employees in Maryland and Texas were on strike through the work day to "tell Microsoft to stop dragging their feet" when it comes to worker demands about job security and improved conditions.

Concerns of strikers included requiring workers who had been working from home some or all of the time to return to offices, according to the union.

"We respect our employees' rights to express their point of view as they have done today," a Microsoft spokesperson said in response to an AFP inquiry.

"We will continue to listen and address their concerns at the bargaining table. "

Software giant Microsoft acquired ZeniMax Media for $7.5 billion in 2021, marking a major expansion for its Xbox division that gave it ownership of several best-selling franchises.

ZeniMax is the parent company of Bethesda Softworks, publisher of the Fallout and Elder Scrolls franchises.

Workers at Bethesda Game Studios joined the CWA in July of this year as union organizing gained momentum in the face of grueling work loads and scant job security.

Bethesda Game Studios employees joined "a surge of workers" forming unions in the video game industry, according to the CWA, which lists members at SEGA of America, Activision Blizzard, ZeniMax, and Tender Claws.