Ntwali was the sole fatality in a car accident in Kigali on Wednesday, police spokesman John Bosco Kabera told Reuters. The driver of the other vehicle has been arrested and "the accident file is being processed for onward transmission to prosecution," Kabera said.
Ntwali had been away from work since Monday, The Chronicles said.
Human rights activists and journalists outside Rwanda raised questions about the official narrative, noting how critics of President Paul Kagame's government have repeatedly been arrested, threatened, or gone missing.
Government spokeswoman Yolande Makolo did not immediately respond to requests for comment.
Ntwali "joins a sinister list of people who have challenged the government and died in suspicious circumstance," said Lewis Mudge, Central Africa director at Human Rights Watch.
"There are many reasons to question the theory of a car accident and it is essential that a prompt, effective investigation, drawing on international expertise, be conducted to determine whether or not he was murdered."
The Rwandan government has previously denied accusations that it kills critics or commits human rights abuses.
In 2014, the US State Department rebuked Rwanda for what it called a "succession of what appear to be politically motivated murders of prominent Rwandan exiles."
Williams, who had been arrested several times before, was an editor at The Chronicles and ran YouTube channel Pax TV - IREME News.
He reported on issues including arrests of opposition figures, deaths of critics and forced evictions.
Last year, while reporting on evictions, he told Al Jazeera: "I'm focused on justice, human rights, and advocacy... the three are risky here in Rwanda. But I'm committed."
"Those who try to speak out, they are jailed - harassed, intimidated or jailed. Second, forced to flee their country. Three, some of them disappear in thin air. Or even, they die."
Human Rights Watch said last year that authorities were threatening and prosecuting Rwandan journalists and YouTubers.
The US State Department's 2014 rebuke followed the killing in Johannesburg of Rwanda’s former spy chief who had become a critic of Kagame.
In 2021, opposition figure Seif Bamporiki was killed in an apparent robbery in South Africa and government critic Cassien Ntamuhanga disappeared after being arrested in Mozambique, where he had sought asylum.
Rwanda's government has denied involvement in all of those cases.
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