Samsung Electronics chairman Lee Kun-hee, who transformed the South Korean firm into a global tech titan, died at the age of 78 on Sunday, the company said.

Under Lee's leadership, Samsung rose to become the world's largest producer of smartphones and memory chips, and the firm's overall turnover today is equivalent to a fifth of South Korea's GDP.

Samsung's meteoric rise helped make Lee South Korea's richest and most powerful industrialist.

"It is with great sadness that we announce the passing of Kun-hee Lee, Chairman of Samsung Electronics," the company said in a statement.

"Chairman Lee passed away on October 25 with his family, including Vice Chairman Jay Y. Lee, by his side.

"Chairman Lee was a true visionary who transformed Samsung into the world-leading innovator and industrial powerhouse from a local business," the firm said, adding: "His legacy will be everlasting."

Samsung is by far the biggest of the family-controlled conglomerates, or chaebols, that dominate business in South Korea.

They drove the nation's transformation from a war-ravaged ruin to the world's 12th-largest economy, but nowadays are accused of murky political ties and stifling competition -- with Lee himself twice convicted of criminal offences, in one case bribing a president.

- Global power -
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.

But it was seen as a shoddy producer of cheap, low-quality products.

"Let's change everything except our wives and kids," Lee said in 1993.

The company gathered up and burnt all 150,000 mobile phones it had in stock, paving the way for the rebirth of the highly successful "Anycall" handset.

With Lee at the helm, Samsung became a global behemoth: by the time he suffered a heart attack in 2014, it was the world's biggest maker of smartphones and memory chips, and a major player in semiconductors and LCDs.

Lee rarely spoke to the media, but was closely watched whenever he broke his long silences, often with doom-laden New Year corporate addresses.

His son, Samsung Electronics vice chairman Lee Jae-yong, has been at the helm of the company since the 2014 heart attack.

- 'Hermit king' -
Despite his immense wealth and power, Lee seldom ventured out from the high walls of his private compound in central Seoul to visit the company headquarters, earning him the nickname "hermit king".

Lee, the third son of Samsung group founder Lee Byung-chull, had a soft spot for dogs -- developed as a child in Japan where he went to school from age 11. He was also known for his love of movies, horseriding and exotic supercars.

He studied at Japan's prestigious Waseda University and earned an MBA at George Washington University in the United States.

He became vice chairman of the group's construction and trading arm at the age of 36, and became group chairman nine years later, shortly after his father's death.

Lee married Hong Ra-hee -- whose father was a justice minister -- with whom he had a son and three daughters.

- Bribes, embezzlement, tax evasion -
The worlds of politics and business have been intertwined in South Korea, and the connection was reflected in Lee's career.

In 1996, he was convicted of bribing former president Roh Tae-woo to get favours for Samsung in business policy decisions.

Lee was also found guilty of embezzlement and tax evasion in a slush fund scandal in 2008, which saw him briefly step down from the company leadership.

But suspended sentences meant he never served time in jail and he received two presidential pardons, going on to spearhead his country's successful efforts to secure the 2018 Winter Olympics.

A few years later, he fought off a lawsuit from his older brother and sister claiming they were entitled to Samsung shares worth billions of dollars.

He had been in medical care after his heart attack, but few details were ever revealed about his condition, leaving him shrouded in mystery even in his final days.