The aircraft, which had been on a visit to troops deployed in northwest Kenya to combat endemic cattle-rustling, came down just minutes after leaving Cheptulel Boys Secondary School in West Pokot County, Ruto said.
Two soldiers survived the crash and were in hospital, he said, adding that an air investigation team had been sent to discover the cause.
"Our motherland has lost one of her most valiant generals," Ruto told a news conference.
"The demise of General Ogolla is a painful loss to me."
Ogolla was previously the head of the Kenyan air force, before rising to deputy military chief and then being promoted by Ruto last year to head the military.
Ogolla joined the Kenya Defence Forces in 1984, where he trained as a fighter pilot with United States Air Force and as an instructor pilot at the Kenya Air Force (KAF), according to a Defence Ministry profile.
When promoting Ogolla to the top military job a year ago, Ruto accused him of being part of a plot to overturn the result of the 2022 presidential election but said he was the best qualified person for the job.
Dozens of civilians and police officers have been killed in the unrest in the northwest.
At least 10 soldiers were killed in June 2021 when their helicopter crashed while landing near the capital Nairobi.
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