Unionized workers of Samsung Electronics launched their first-ever strike Monday, demanding higher pay and warning of potential further action if the country's largest conglomerate does not meet their demands.

The National Samsung Electronics Union, the biggest labor union of the conglomerate with over 30,000 members, making up some 25 percent of the workforce, said it kicked off the three-day strike starting with a rally at 11:00 a.m. in front of the main entrance of the company's plant in Hwaseong, Gyeonggi Province.

This strike is the first held since the establishment of Samsung Electronics in 1969. The strike is scheduled to last through Wednesday.

The union said that 6,540 members are participating in the strike, of which 5,211 workers are reportedly in semiconductor facilities, manufacturing and development. Due to the heavy rain on Monday, the union said around 4,000 people actually attended the rally on-site, but the crowd is reported to have packed the five-lane road in front of the entrance gate.

The total number of union members was 36,570 as of 11 a.m., exceeding the 30,000 threshold for the first time, the union said.

Since January, several rounds of negotiations have taken place, but both sides have remained at an impasse over wages, the vacation system and bonuses.

After securing the right to strike when the National Labor Relations Commission decided to suspend mediation and have the members of the union vote for and against the strike, the union declared the collective action for the first time on May 29.

The union had previously demanded a higher wage increase for all members, fulfillment of the paid leave promises and improvement in the standards for performance incentives based on economic value added, or EVA, a financial metric estimating a firm's financial performance by deducting invested capital from operating profit, as well as compensation for wages lost during the strike.

"The company did not accept all of our demands during the two weeks of post-arbitration talks after June 13," said the union.

"The company's post-arbitration plan does not consider workers as being on equal terms and still treats them like expendable items," the union stated.

"We are holding the company accountable for all of this through a strike," it said, adding, "The company is solely responsible for all business losses incurred as a result of this strike."

As there were no production disruptions as feared with last month's collective action when union members coordinated taking their annual leave in order effectively to stage a mass walkout, it is widely believed that this week's strike is unlikely to impact business activity.

The union said it is open to a second strike for five days from next Monday if the negotiations do not progress during this strike.