The columnists include George Kegoro, executive director of the Kenyan Human Rights Commission; Lynne Muthoni Wanyeki, Africa director of the Open Society Foundation; and Nic Cheeseman, professor of democracy at Birmingham University.
“I resign to protest the growing infringement on media freedom. I resign to show solidarity with the voices that have been silenced. I resign because we must live our beliefs,” Cheeseman wrote on Twitter.
In a joint statement, the eight highlighted several incidents in recent years that they said pointed to meddling in the independence of the Nation Media Group (NMG).
These included the firing of a managing editor after an editorial critical of the presidency and failing to renew the contract of popular cartoonist Gado who regularly took aim at government.
Last month, NMG sacked the manager of its NTV station, Linus Kaikai, after he said there had been collusion between media owners and government to censor coverage of the mock swearing-in of opposition leader Raila Odinga, who maintained he won elections last year.
NTV and two other television stations were pulled off air for a week — despite court orders directing they be put back on — as they attempted to cover the ceremony.
The media suspension was attacked by the UN, the United States and rights watchdogs.
“A worrying pattern has emerged where it appears the executive [government] is able to influence who works for or contributes to NMG,” read the joint statement.
“Censoring individual columnists signals official intolerance for dissenting views and suggests executive willingness to go to any length — even co-opting editors — to achieve its aims.”
The NMG is the biggest private media house in East Africa, operating in Kenya, Uganda, Tanzania and Rwanda.
The group responded to the mass resignation “with regret” and assured readers they remained “committed to media freedom”.
“We wish to reiterate that overall we have honoured our obligation to respect their views and did not tamper with their positions except to correct basic errors,” the group said in a statement.
Kenya is recovering from a damaging election season in 2017 which saw a first vote overturned by the Supreme Court, and a second boycotted by Odinga who claimed the election would not be free and fair.
Protests during the crisis left at least 92 dead, mostly shot by police, according to rights activists.
In a surprise move earlier this month, President Uhuru Kenyatta and Odinga shook hands and vowed to reconcile in a bid to heal divisions — a decision which has thrown the opposition NASA coalition into disarray.