Samsung had previously earmarked $1 billion for the display assembly plant in Vietnam, which began production in the first quarter. Reuters

Samsung Display, a subsidiary of Samsung Electronics Co. Ltd., plans to invest an additional $3 billion to boost the production capacity of its display module assembly plant in Vietnam, a report said Friday, citing a source familiar with the matter.

The additional capital will increase the total investment by Samsung Display in the Southeast Asian country to $4 billion. The South Korean conglomerate earlier earmarked $1 billion for the new OLED display module assembly facility in Bac Ninh province, located in the Red River Delta in the country's north, Reuters reported, adding that the plant began production in the first quarter.

The extra $3 billion will be spent over several years until 2020, the source told Reuters, without providing more details about the investment. In November, Samsung also reportedly applied for approval to invest $3 billion for building a second smartphone factory in northern Vietnam.

Samsung Display’s annual capital spending has averaged 3.9 trillion won ($3.4 billion) in the past three years. The company also expects its revenue to touch $40 billion in 2018 and $60 billion by 2020, local media reported.

Samsung was recently reported to be creating a standalone team to work exclusively on screens for Apple products.

The company is said to be relying more on its display and semiconductor unit as its mobile division’s income has suffered continuous declines over the last few quarters. In the second quarter of 2015, Samsung reported an annual decline of 38 percent in the mobile unit’s operating profit, generating 2.8 trillion won, compared with 4.4 trillion won in the previous year.

Friday’s revelation came nearly four months after media reports said that Samsung would invest at least 10 trillion won more to boost production capacity at a new chip manufacturing plant in South Korea.