A lawyer who exposed a network of secret prisons in war-ravaged Yemen, where thousands of men and boys were arbitrarily held and tortured, on Wednesday received the world's most prestigious human rights prize.

Huda Al-Sarari, 42, was hailed by the Martin Ennals Award jury for showing "rare courage" to investigate, expose and challenge a network of secret prisons established by foreign governments in Yemen since 2015.

That year, the Saudis intervened in Yemen at the head of a military coalition against Iran-backed Huthi rebels, who had seized control of the capital Sanaa.

Since then, the conflict has killed tens of thousands of people, most of them civilians, and sparked what the United Nations calls the world's worst humanitarian crisis.

Al-Sarari received the award, which is often referred to as the Nobel Prize for human rights, for her work exposing "the enforced disappearances that occurred as a result of secret prisons run by foreign governments in Yemen," the award organisers said in a statement.

Within this system "thousands of men and boys have suffered from arbitrary detention, torture and extrajudicial killings," it said.

Al-Sarari "collected evidence on more than 250 cases of abuse taking place within the prisons and succeeded in convincing international organisations such as Amnesty International and Human Rights Watch to take up the cause," they said.

- 'Extremely challenging' -

The lawyer was hailed for pushing on with her pursuit of justice despite threats and defamation campaigns against her and her family.

"Huda Al-Sarari has chosen not to leave Yemen," jury member Alice Mogwe of the FIDH said in the statement.

"That is a decision which shows a rare courage, all the more so as she is working in a high-risk context and a source of danger for herself," she added.

The laureate herself meanwhile stressed the particular challenges she had faced due to her gender.

"Being a human rights defender in Yemen is extremely challenging, and being a woman makes this even more difficult," she said in the statement.

"In a male-dominated society, I have to prove myself maybe 10 times more than a man."

The two runners-up for this year's award -- also both women -- were honoured at Wednesday's ceremony as well.

Norma Ledezma, a Mexican human rights activist was celebrated for her work in fighting femicide and supporting the families of victims after her daughter, Paloma, disappeared on her way home from school in Chihuahua.

Sizani Ngubane, a 73-year-old activist, was meanwhile recognised for her work for women's and indigenous people's rights in South Africa.

The Martin Ennals foundation is named after the first secretary general of Amnesty International and the 50,000 Swiss franc ($50,800, 47,000 euros) prize is judged by the London-based rights group, along with Human Rights Watch and other leading organisations.

Al-Sarari said the prize "gives me great strength and emboldens me to continue this fight for justice."

"I believe the award will be incredibly important in drawing attention to the continual plight of victims of arbitrary detention, abuse and torture in Yemen."

The other finalists were awarded 20,000 Swiss francs each from the foundation.