The family of Nigerian novelist Chimamanda Ngozi Adichie has accused a hospital of negligence over the death of her 21-month-old son.

Nkanu Nnamdi died at a hospital in Nigeria on Wednesday following a short illness, leaving the family of the acclaimed postcolonial feminist writer "devastated".

Now, the family allege there was a litany of failures at Euracare Hospital in Lagos that led to the toddler's death, including being denied oxygen and being given too much sedation, causing a heart attack.

The hospital expressed its "deepest sympathies" over the loss of the child but denied improper care, which it said had been in line with international standards.

It added that Nkanu had arrived at the hospital "critically ill" and that an investigation into the death was now under way.

Adichie's sister-in-law, Dr Anthea Nwandu, made a series of allegations about the hospital in an interview with Nigerian broadcaster Arise TV on Saturday.

In it, she said the medical director of Euracare had told Adichie her son "had received too much sedation", which subsequently caused him to have a heart attack.

Dr Nwandu also accused medical staff of leaving the child unattended, denying him oxygen and transporting him in a manner that was "not according to standard practice".

She alleged Nkanu suffered a brain injury due to lack of oxygen.

Similar accusations concerning Nkanu's care were made in a private message from Adichie that was leaked online.

Her spokeswoman Omawumi Ogbe told the BBC that the message had originally been shared within "a close circle of family and friends", and "was not for public consumption".

Ms Ogbe continued: "While we are saddened that such a deeply personal account of grief and trauma was leaked, the details therein highlight the devastating clinical failures the family is now forced to confront.

"We hope that the substance of that message, detailing the gross medical negligence that led to this tragedy remains the central focus even as we look forward to the truth and accountability."

Nkanu was one of twin boys Adichie shared with her husband, Dr Ivara Esege.

Responding to the allegations, Euracare Hospital acknowledged the "profound and unimaginable loss" the family was experiencing, but said in a statement on Saturday that "reports currently being circulated contain inaccuracies".

It said Nkanu, who was critically ill, had been referred to the hospital after receiving treatment from two paediatric centres, and that upon arrival staff "immediately provided care in line with established clinical protocols and internationally accepted medical standards, including the administration of sedation".

It continued: "In the course of his care, we worked collaboratively with external medical teams as recommended by his family and ensured that all necessary clinical support was provided."

However, "despite these concerted efforts", the boy died less than 24 hours after arriving at the hospital, it added.

A "detailed investigation" was under way, Euracare said, adding that it remained "committed to engaging transparently and responsibly with all clinical and regulatory processes".

Adichie, 48, had her first child, a daughter, in 2016. Her twin boys were born using a surrogate in 2024.

The award-winning US-based writer is known for works including Half of a Yellow Sun, Americanah and her 2012 Ted Talk and essay We Should All Be Feminists, which was sampled by Beyoncé on her 2013 song Flawless.

Nigeria's president was among those to have expressed their condolences over the death of Nkanu.

The African nation's health system has suffered of late from a severe shortage of doctors, leaving healthcare staff working long hours and doctors juggling jobs in both public and private hospitals.

Responding to the allegations concerning Nkanu, an adviser to the Lagos State government said it "places the highest value on human life and maintains zero tolerance for medical negligence or unprofessional conduct".

Dr Kemi Ogunyemi, Special Adviser to the Lagos State Governor on health matters, confirmed the state's health watchdog had commenced a "thorough, independent and transparent" investigation into the circumstances surrounding the death.

"Any individual or institution found culpable of negligence, professional misconduct, or regulatory violations will face the full wrath of the law," Dr Ogunyemi said.

She urged members of the public to avoid speculation over the death while the official investigation was ongoing.