It was not immediately clear what caused the crash.

Gen Ogolla was among 12 occupants of the military aircraft that went down on Thursday afternoon shortly after take off in the north-west of the country.

The bodies of those who died were flown to Nairobi and the two survivors are being treated in hospital.

The four-star general will be buried on Sunday at his home in western Siaya county, his family has said.

Announcing three days of national mourning, President William Ruto said the deaths were a "moment of great sadness" for the country.

Getty Images

Gen Ogolla was appointed Kenya's Chief of Defence Forces in April last year.

Mr Ruto described his chief military adviser as a gallant officer who had died in the line of duty.

"Our motherland has lost one of her most valiant generals, gallant officers, service men and women," Mr Ruto told the nation.

Gen Ogolla first joined the Kenya Defence Forces on 24 April 1984, according to the Kenyan defence ministry's website.

He was due to mark 40 years in the military next week.

He began his career as a 2nd lieutenant in the country's air force, where he trained as a fighter pilot with the US air force, the ministry says. The late general also trained in imagery intelligence, counter-terrorism and accident investigation.

In 2018, he became commander of the air force.

In an interview last May, Mr Ruto said he appointed Gen Ogolla as the army chief "against the advice of many people". The president said Gen Ogolla was among a group who tried to influence the 2022 presidential election results.

Image:EPA - Kenya is observing three days of mourning following the deaths of the military personnel.

This is the first time that a Kenyan military chief has died in office.

The nine others killed in the crash were named as Brig Swale Saidi, Col Duncan Keittany, Lt Col David Sawe, Maj George Benson Magondu, Capt Sora Mohamed, Capt Hillary Litali, Snr Sgt John Kinyua Mureithi, Sgt Cliphonce Omondi, and Sgt Rose Nyawira.

Kenyan opposition leader Raila Odinga described the crash as a "terrible day for Kenya".

Moussa Faki Mahamat, chair of the African Union Commission, said its "thoughts and prayers" went out to Kenya's president, government and people following the "tragic helicopter accident".

The officers had travelled to Kenya's North Rift region, which has been plagued by banditry.

They were on a mission to reopen some of the schools closed following bandit attacks. They had also visited military officers deployed to stabilise the region.

In June 2021 at least 10 soldiers were killed when their helicopter crashed while landing near the capital, Nairobi.

The crash was the fifth military aircraft accident in just 12 months, according to Kenya's Standard newspaper.

Maintenance has always been a problem for the military because of the multiple aircraft purchased from different foreign sources, Andrew Franklin, a former US marine and security expert based in Kenya, tells the BBC.

Each aircraft model needs different spare parts, which can be expensive and have tedious inventory processes, he says.

As Kenya's military expenditure is strictly confidential, it is difficult to have oversight on how the money is spent, Mr Franklin adds.

The defence ministry is not obliged by law to submit annual reports to the president or parliament for scrutiny.

The aircraft transporting Gen Ogolla was one of six Bell UH-1H Huey II helicopters acquired by the army from the US in 2016, according to the Star newspaper.

It was brought in to strengthen the military's capabilities in counter-terrorism operations.

The incident raises concerns over the safety and protection of senior military personnel, says Javas Bigambo, a governance expert.

He agrees that there is a need for more accountability when it comes to military spending.