A US-based advocacy group has filed a petition with the United Nations demanding the immediate release of Al Jazeera journalist Mahmoud Hussein as Egyptian authorities extended his detention for another 45 days.

The Robert F Kennedy Human Rights organisation filed a petition for relief on Saturday with the UN's Working Group on Arbitrary Detention, citing the violation of Hussein's basic rights and challenging the unsubstantiated preliminary charges levied against him.

"This regime has embarked on a systematic crackdown on civil society, and Egypt has become one of the most dangerous places on Earth to be a journalist," said Kerry Kennedy, president of the organisation.

Hussein, an Egyptian based in Qatar, was stopped, questioned, and arrested by Egyptian authorities in December 2016 after travelling to Cairo for a holiday.

Since then, his detention has been renewed six times. The latest renewal was made on Saturday for another 45-day period.

Hussein is accused of "incitement against state institutions and broadcasting false news with the aim of spreading chaos".

He was held in solitary confinement for 89 consecutive days and has been, to date, detained without formal charges for 130 days.

Hussein's daughter, Zahra, said earlier this month that he suffers from harsh and inhumane conditions that have led to a deterioration in his health and caused him shortness of breath.

She said the problems began during his 89 days in solitary confinement in a small cell in Tora prison without heat, water, or electricity.

Robert F Kennedy Human Rights recently filed a similar petition demanding the release of activist Aya Hijazi, an Egyptian-American charity worker who was released from an Egyptian prison earlier this month after spending three years in detention.

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Human rights and media organisations have denounced Hussein's detention and called for his immediate release.

Al Jazeera has demanded that Egypt unconditionally release Hussein and condemned the continued renewal of his detention.

The network says it holds the Egyptian authorities responsible for Hussein's safety and wellbeing, rejects the allegations against him, and condemns those who forced him into false "confessions" made on video.

The UN has called on Egypt to comply with its commitment to protect freedom of expression.

In January, Stephane Dujarric, spokesman for the UN secretary-general, said: "We appeal for this case to be resolved in accordance with Egypt's own international obligations to protect freedom of expression and freedom of opinion."

Over the past few years, Egyptian authorities have arrested several Al Jazeera employees, raising concerns over media freedom in the country.

In May, a Cairo court sentenced a former editor-in-chief of Al Jazeera Arabic, Ibrahim Helal, to death, charging him in absentia with endangering national security.

Al Jazeera's Baher Mohamed, Mohamed Fahmy, and Peter Greste - along with seven colleagues outside the country - were accused of spreading "false news" during their coverage of the aftermath of the military overthrow of then-president Mohamed Morsi in 2013, the year they were taken into custody.

Mohamed and Fahmy spent 437 days in jail before being released. Greste spent more than a year in prison.

The judge who sentenced the journalists said they were brought together "by the devil" to destabilise the country.

Hussein joined Al Jazeera in Egypt in 2011. He moved to the network's headquarters in Doha in 2013.