A union representing tens of thousands of workers at South Korean tech giant Samsung Electronics told Agence France-Presse (AFP) on Tuesday it would hold a three-day strike later this month after negotiations failed.

"Starting from July 8, we will stage a three-day general strike," Lee Hyun-kuk, vice president of the National Samsung Electronics Union, told AFP.

The union announced the strike late Monday in a live YouTube broadcast, without providing the dates.

The move follows a one-day walkout in June, the first such collective action at the company, which went decades without unionization.

Management at the company, the world's biggest producer of memory chips, has been locked in negotiations with the union since January.

Workers have rejected the offer of a 5.1% pay hike, with the union having previously outlined demands including improvements to annual leave and transparent performance-based bonuses.

In calling for the strike, the union said that "management created this state" by failing to offer significant concessions.

"What will change if we do not act. Will you just watch and do nothing? Will you be a hidden slave or an active owner? Nothing will change if we do not act," its statement said.

"All employees need to participate in the strike. Let's step up and change it!"

Samsung declined a request for comment.

Samsung Electronics avoided its employees unionizing for almost 50 years - sometimes adopting ferocious tactics, according to critics – while rising to become the world's largest smartphone and semiconductor manufacturer.

Company founder Lee Byung-chul, who died in 1987, was adamantly opposed to unions, saying he would never allow them "until I have dirt over my eyes."

The first labor union at Samsung Electronics was formed in the late 2010s.