What you need to know:
- Security forces arrested EIPR office manager Mohamed Basheer on Sunday, before detaining researcher Karim Ennarah on Wednesday and executive director Gasser Abdel-Razek on Thursday.
- The OHCHR said the arrests "appear to have been carried out as retaliation" because they came after the EIPR hosted a meeting with 13 ambassadors and diplomats.
The UN on Friday urged Egypt to release three members of a rights group arrested within days of each other, adding to international pressure on the country over the case.
In a fresh wave of an ongoing crackdown, the Egyptian Initiative for Personal Rights (EIPR) was targeted after several ambassadors and diplomats visited its Cairo office on November 3.
Security forces arrested EIPR office manager Mohamed Basheer on Sunday, before detaining researcher Karim Ennarah on Wednesday and executive director Gasser Abdel-Razek on Thursday.
They were held on charges including "joining a terror group" and "spreading false news", the EIPR said, and placed in pre-trial detention for 15 days -- which under Egyptian law can be extended and last up to two years.
"The arrest of three human rights defenders in Egypt this week is a very worrying development that underscores the extreme vulnerability of civil society activists," the UN High Commissioner for Human Rights (OHCHR) said in a statement.
"We are very concerned that the targeting of human rights defenders and other activists... are having a profound chilling effect on an already weakened Egyptian civil society," added spokesperson Ravina Shamdasani.
The OHCHR said the arrests "appear to have been carried out as retaliation" because they came after the EIPR hosted a meeting with 13 ambassadors and diplomats.
Similar concerns have poured in from traditional allies of Egypt, including the United States and United Kingdom.
"Meeting with a wide range of interlocutors, including members of civil society, is an integral part of normal diplomatic practice in every country," Irish ambassador Sean O Regan tweeted on Friday.
His Italian counterpart and other ambassadors sent a letter to Egyptian Foreign Minister Sameh Shoukry calling for the release of the EIPR staff, Italian news agency Adnkronos reported Friday.
British Foreign Secretary Dominic Raab also raised the issue with Shoukry, the Foreign Office said.
The US State Department said Washington was "deeply concerned" on Thursday.
US President Donald Trump has stood firmly behind Egyptian President Abdel Fattah al-Sisi, whom he reportedly called "my favorite dictator," but President-elect Joe Biden has signalled he will take a firmer line on human rights.
Delaware Senator Chris Coons, a potential pick in Biden's incoming administration, tweeted on Friday that the arrests were "another disturbing example of Egypt's crackdown on human rights activists".
There have been no immediate reactions from Egypt.
But on Wednesday the foreign ministry had rejected criticism from France after Basheer's arrest, with spokesman Ahmed Hafez accusing Paris of "meddling" in Egypt's domestic affairs.
Rights groups estimate that some 60,000 detainees in Egypt are political prisoners.
These include secular activists, journalists, lawyers, academics and Islamists arrested in a sweeping crackdown on dissent under Sisi.