Jailed British-Egyptian activist Alaa Abdel Fattah has ended a months long hunger strike, his family said Tuesday, after fears for his health grew and amid criticism of Cairo during the ongoing COP27 climate summit.

Abdel Fattah, who consumed "only 100 calories a day" for seven months, escalated his strike, first to all food, then water as the COP27 climate summit opened on November 6 in the Egyptian resort town of Sharm el-Sheikh.

"I have ended the strike," the activist wrote in the letter handed to his family on Tuesday, but dated the day before, shared by his sister Mona Seif.

Abdel Fattah, 40, wrote to his mother, "I want to celebrate my birthday with you on Thursday".

He asked her to "bring a cake" to her monthly visit to the Wadi al-Natroun prison, about 100 kilometres (60 miles) northwest of the capital Cairo.

A key figure in the 2011 uprising that toppled longtime autocrat Hosni Mubarak, Abdel Fattah has spent much of the past decade since behind bars.

He is currently serving a five-year sentence for "spreading false news" by sharing a Facebook post about police brutality.

He has been leading headlines since the UN climate talks began last week in Egypt, which sought to burnish its image by hosting COP27 but has come under fire over its human rights record.

International pressure has mounted since world leaders began arriving in Sharm el-Sheikh last week. Several raised the case in bilateral meetings with President Abdel Fattah al-Sisi, most recently US President Joe Biden on Friday.

Activists have posted widely on Twitter under the hashtag #FreeAlaa, and several speakers at the summit ended with the words "you have not yet been defeated" -- the title of Abdel Fattah's book published while behind bars.

Fears had mounted that prison authorities were force-feeding Abdel Fattah, after his mother was notified he had been put "under medical supervision".

His sister Sanaa Seif was repeatedly heckled by pro-government attendees as she campaigned for his release at COP27, including one member of parliament who had to be escorted out by UN security.

On Friday, Mona Seif said the family had submitted a new request for a presidential pardon.

The plea was picked up by one of Egypt's most watched talk show hosts, the ardently pro-Sisi Amr Adib.

On prime time television Friday, Adib said the pardon would be in "the interest of Egypt first and foremost".