PARIS (Reuters) - "Assassin's Creed" maker Ubisoft faced a union call for three days of strike action on Thursday after the French videogame group told workers to return to the office.

Ubisoft told its employees that they would be required to go to the office three days a week, the STJV videogame workers' union said, adding that the company's demand came after profit-sharing negotiations collapsed.

The company declined to comment.

"After more than five years of working efficiently in the current remote-work context, many of our colleagues have built or rebuilt their lives (family life, housing, parenthood, etc.) and simply cannot return to the previous working conditions," the union said in a statement.

It said the strike would take place on Oct. 15-17.

Ubisoft's shares dropped by more than 17.5% after it postponed the release of "Assassin's Creed Shadows" by three months on Wednesday and cut its net bookings guidance.

The company had been counting on the Assassin's Creed game and "Star Wars Outlaws", which was released to a tepid reception, to improve its fortunes after four years of negative cash flow, game cancellations and delays.

Separately, an activist investor pushing for a sale Ubisoft has gathered support from 10% of its shareholders, it said in a letter on Thursday that was exclusively shared with Reuters.

(Reporting by Michal Aleksandrowicz and Florence Loeve in Paris; Editing by Makini Brice and Alexander Smith)