The family of Egypt's jailed dissident Alaa Abdel Fattah said Thursday prison authorities had told them he is "under medical intervention", as fear mounts that means force-feeding.
The family have repeatedly demanded information on the health of the British-Egyptian activist in recent days after he escalated his months-long hunger strike to include water too.
His mother Laila Soueif, at the Wadi al-Natroun prison north of Cairo, was informed that "medical intervention was taken" with Abdel Fattah "with the knowledge of judicial entities", his sister Mona Seif wrote on Twitter.
"They should allow our mother to see him immediately and see for herself how he is," Seif added.
Abdel Fattah, a veteran pro-democracy and rights campaigner, is serving a five-year prison sentence for "spreading false news" by sharing a Facebook post about police brutality.
International concern has mounted since Abdel Fattah, 40, also began declining liquids since Sunday, the start of the UN climate summit COP27 hosted by Egypt.
Since then, his mother had visited the Wadi al-Natroun prison about 100 kilometres (60 miles) from Cairo, pleading for news.
On Thursday, an officer told her that her son was "under medical intervention", but gave no other details.
Hossam Bahgat, founder of the Egyptian Initiative for Personal Rights (EIPR), the country's largest rights group, said the prison officer statement "means he is being force-fed".
'Hidden behind high walls'
A key figure of the 2011 uprising that toppled longtime autocrat Hosni Mubarak, Abdel Fattah gained British citizenship this year.
"Surely our mother should see him, or someone from @UKinEgypt (British embassy in Cairo) so we understand his real health status!!" Seif added on Twitter.
The dissident's aunt, novelist Ahdaf Soueif, earlier this week said the family was concerned about "rumours of force-feeding and of sleep-inducing drugs".
She demanded that the British-Egyptian activist be moved to the Qasr al-Aini University Hospital, Cairo's largest state medical facility, and given access to lawyers and British embassy officials.
She said she feared "the prison hospital is probably not equipped" to care for a patient who has been living for months "on 100 calories a day".
British Prime Minister Rishi Sunak, French President Emmanuel Macron and German Chancellor Olaf Scholz have all voiced concern and called for his release.
United Nations rights chief Volker Turk has warned Abdel Fattah's "life is in great danger".
Activists at COP27 summit in Egypt's Red Sea resort of Sharm el-Sheikh have posted widely on Twitter under the hashtag #FreeAlaa, and several speakers have ended with the words "you have not yet been defeated" -- the title of the jailed activist's book.
On Thursday, hundreds of COP27 participants, dressed in white like Egyptian prisoners, chanted "Free him!" and "no climate justice without human rights!".
Others shouted "Free them all!" in reference to the 60,000 political detainees rights groups say are incarcerated in the country, many of them in brutal conditions and overcrowded cells -- accusations which Cairo rejects.
"We are carrying out this action to draw attention to those who are invisible, hidden behind high walls, incarcerated in the country hosting COP27 -- and all over the world," one of the organisers George Galvis said.
The issue is intensely sensitive in Egypt, ranked 135 out of 140 countries in the World Justice Project's rule of law index.
As international criticism mounts, a counter-campaign has grown.
One Egyptian lawmaker protested during a press conference by Sanaa Seif, Alaa Abdel Fattah's other sister, at COP27 -- before being expelled by UN security -- and another has called on parliament to protest.
Egypt's mission in Geneva slammed the intervention by the UN's Turk, saying his "characterisation of a judicial decision as 'unfair' is an unacceptable insult".
A lawyer has also filed a complaint against Sanaa Seif for "conspiracy with foreigners" and "false information", according to campaigners calling for Abdel Fattah to be freed.
The prosecution has yet to decide on the complaint, the same potential charge of spreading "false information" that Abdel Fattah was himself jailed for.
He had shared a post -- written by someone else -- accusing an officer of killing an inmate under torture.