Samsung Electronics Co. Chairman Lee Kun-hee, 78, passed away at a hospital in Seoul on Sunday after being hospitalized for six years following a heart attack, the company said in a statement.

"It is with great sadness that we announce the passing of Lee Kun-hee, Chairman of Samsung Electronics," according to the statement.

When Lee inherited the chairmanship of the Samsung group in 1987 – founded by his father as a fish and fruit exporter – it was already the country's largest conglomerate, with operations ranging from consumer electronics to construction.

Under Lee's leadership, Samsung rose to become the world's biggest technology firm by revenue – seeing off Japanese brands Sony, Sharp Corp. and Panasonic Corp. in chips, TVs and displays; ending Nokia Oyj's handset supremacy and beating Apple Inc. in smartphones.

Samsung is by far the biggest of the family-controlled conglomerates, or chaebols, that dominate business in South Korea, the world's 12th-largest economy.

"Chairman Lee was a true visionary who transformed Samsung into the world-leading innovator and industrial powerhouse from a local business. His 1993 declaration of 'New Management' was the motivating driver of the company's vision to deliver the best technology to help advance global society," Samsung said in a statement.

He died with his family by his side, including his son, Samsung Electronics Vice Chairman Lee Jae-yong, the conglomerate said.

The death of Lee, with a net worth of $20.9 billion according to Forbes, is set to prompt investor interest in a potential restructuring of the group involving his stakes in key Samsung companies such as Samsung Life and Samsung Electronics.

Lee owns 20.76 percent of the insurance firm and is the biggest individual shareholder of Samsung Electronics with a 4.18 percent stake.

Lee's son Lee Jae-yong has been embroiled in legal troubles linked to a merger of two Samsung affiliates that helped Lee assume greater control of the group's flagship Samsung Electronics.

The younger Lee has been at the helm of the company since 2014. He was jailed for five years in 2017 after being found guilty of bribery and other offenses linked to former President Park Geun-hye, before being cleared of the most serious charges on appeal and released a year later. That case is currently being retried.

"With Lee passing, Samsung Group is now facing the biggest governance shakeup since the merger between Cheil Industries and Samsung C&T" in 2015, said Ahn Sang-hee, an expert in corporate governance at Daishin Economic Research Institute.

It remains unclear how the elder Lee's three children will split his wealth, an issue that has led to family feuds at other chaebols in recent years after the death of their patriarchs.

Samsung did not specify the cause of death and declined to comment on whether Lee left a will.

(With input from agencies)