A leading human rights group in Egypt says security forces have detained two members of its staff in recent days.
The Egyptian Initiative for Personal Rights reported that its director of criminal justice, Karim Ennarah, was arrested on Wednesday in Dahab and taken to an undisclosed location.
Its office manager, Mohammed Basheer, was detained in Cairo on Sunday.
Amnesty International condemned what it called the "chilling escalation" of a crackdown on civil society in Egypt.
Human rights groups say dozens of activists have been targeted with arrests, travel bans and asset freezes under President Abdul Fattah al-Sisi.
Mr Sisi led the military's overthrow of his democratically elected predecessor Mohammed Morsi in 2013 following protests against his rule.
The EIPR is an independent human rights group whose work covers a variety of political, civil, economic and social issues in Egypt.
On Sunday, the EIPR issued a statement saying security personnel had raided Mr Basheer's home overnight and taken him to a State Security Sector facility, where he was questioned about a visit on 3 November by senior Western diplomats to the EIPR's Cairo office to discuss human rights.
He was later taken to the Supreme State Security Prosecution (SSSP) and asked about the EIPR's work, its latest publications and its legal aid work, the statement added.
Mr Basheer was accused of charges including "joining a terrorist organisation" and "spreading false news", and added to an SSSP case involving investigations over what Amnesty International said were unfounded terrorism-related charges against other human rights defenders..
The EIPR said prosecutors did not present Mr Basheer with any reliable evidence and demanded his immediate release.
On Wednesday afternoon, the EIPR tweeted that Mr Ennarah had been arrested by National Security officers in Dahab, a Red Sea resort in South Sinai province, and that his whereabouts were unknown.
There was no immediate comment from the Egyptian authorities.
#Egypt: Amnesty International strongly condemns the security forces’ outrageous arrest of Karim Ennarah, director of criminal justice at @EIPR from South Sinai, where he was on vacation. His whereabouts remain unknown (1/3) pic.twitter.com/H5g9yVVqq8— Amnesty MENA (@AmnestyMENA) November 18, 2020
"These arrests, following a meeting at EIPR with Western diplomats, serve a heavy blow against the legitimate work of human rights defenders," Amnesty International tweeted.
"Time for the international community to call on Egypt to end reprisals against human rights organizations and release EIPR staff now," it added.
France expressed "deep concern" over the arrest of Mr Basheer on Tuesday, and stressed that it maintained "a frank, exacting dialogue with Egypt on human rights issues".
The Egyptian foreign ministry on Wednesday rejected France's "interference in an Egyptian internal affair and the attempt to influence the investigations". It also stressed that Egypt respected the rule of law and equality before it.