The pardons announced by the justice minister come amid South Koreans' growing discontent over the conduct of the family-run conglomerates, known as chaebol, that dominate Asia's fourth-largest economy.

The heavy-handed conduct of South Korea's rich and powerful made headlines worldwide with last December's "nut rage" case, after the daughter of an airline chairman took offence at the way she had been served macadamia nuts.

SK Group Chairman Chey Tae-won has been in jail since January 2013, serving one of the longest terms ever given to a chaebol boss.

The order to free Chey and other business leaders aims "to give them a chance to develop the country's economy," the justice ministry said in a statement.

President Park told a cabinet meeting, "The pardons have included some businessmen, for the tasks we face, economic revival and job creation."

A spokeswoman for SK Group said Chey's pardon would resolve a management vacuum and help the conglomerate focus on efforts to rejuvenate the economy.

Shares of SK affiliates were broadly higher on hopes the pardon would prompt decisions such as capital investments or acquisitions. SK Innovation Co Ltd rose 6.6 percent, while SK Hynix Inc was up 3.1 percent.

A Gallup Korea poll in late July showed 54 percent of respondents opposed special pardons for chaebol owners, while just 35 percent backed them.

The public is unlikely to be convinced by the government's rationale for the pardons, said Chung Sun-sup, head of corporate analysis firm Chaebul.com, adding that they could undermine trust in the government.

"It doesn't make sense to be calling for reforms by the chaebol and, at the same time, to be lenient towards the wrongdoing of the heads of those chaebol," he said.

South Korea has a long history of pardoning convicted chaebol bosses or suspending sentences.

Over the years, the heads of the Samsung, Hyundai Motor, SK and Hanwha chaebol have been convicted of crimes but received suspended sentences, and later, presidential pardons.

In her 2012 presidential campaign, Park said she would "strictly limit" pardons for powerful tycoons.

But analysts say that agenda has been derailed by a sluggish economy and the reliance of her Saenuri party on support from conservative high earners.

Anti-chaebol sentiment was whipped up by a public feud between two sons of the 92-year-old founder of Lotte Group, South Korea's fifth-largest conglomerate.

(Additional reporting by Joyce Lee; Editing by Tony Munroe and Clarence Fernandez)

By Ju-min Park and Se Young Lee