The leader of a Kenyan starvation sect went on trial for manslaughter on Monday over the deaths of more than 400 of his followers in one of the world's worst cult-related tragedies.

Self-proclaimed pastor Paul Nthenge Mackenzie and dozens of other suspects pleaded not guilty in January to multiple counts of manslaughter, one of several cases against them over what is known as the "Shakahola Forest Massacre".

Mackenzie appeared in a magistrate's court in the Indian Ocean port city of Mombasa along with 93 other suspects, prosecutors and court officials said.

"There has never been a manslaughter case like this in Kenya," prosecutor Alexander Jami Yamina told AFP, adding that they will be charged under a Kenyan law dealing with suicide pacts.

"This is going to be a very unique manslaughter case."

Mackenzie is alleged to have incited his followers to starve to death in order to "meet Jesus" in a case that provoked horror in Kenya and across the world.

He was arrested in April last year after several bodies were first discovered in the remote Shakahola forest that lies inland from the Indian Ocean town of Malindi.

Rescuers spent many months searching the scrubland and have now unearthed around 448 bodies from mass graves.

Autopsies revealed that the majority of victims had died of hunger. But others, including children, appeared to have been strangled, beaten or suffocated.

Previous court documents also said that some of the bodies had their organs removed.

The charge sheet lists 95 defendants -- 55 men and 40 women including Mackenzie's wife.

But one accused woman died in police custody due to "complications related to long term illness and the effects of the fast," Yamina told AFP, adding that she passed away "a month or so ago".

At least 420 witnesses have been prepared by the prosecutors, with hearings scheduled to run for four days until Thursday.

"Due to the gravity of the case, we have prepared well," Yamina said.

Some of the witnesses will present their testimony behind closed doors.

The suspects went on trial last month on charges of terrorism over the Shakahola massacre, and also face separate cases of murder and child torture and cruelty relating to the deaths. Prosecutors say these occurred over the years 2020 to 2023.

In March this year, the authorities began releasing some victims' bodies to distraught relatives after months of painstaking work to identify them using DNA. So far 34 have been returned.