Insulting a religion is illegal in Egypt, but in practice goes unpunished if it does not target Islam or occasionally Christianity.
Ahmadis believe that a 19th century Indian mystic, Mirza Gulam Ahmed, was the Messiah whose coming was predicted by the Muslim Prophet Mohammed. Traditional Muslim scholars consider them heretics.
"The arrest and interrogation of the Ahmadis is only the latest instance of the security apparatus’s abuse of the shameful, vague and unconstitutional provision on ‘contempt of religions,'" the statement said.
Security officials did not have an immediate response.
On Wednesday, parliament extended the emergency law, continuously in place since former president Anwar Sadat's assassination in 1981, for two more years.
The widely criticised extension cancelled some of the law's provisions, such as the government's power to monitor all communications and censor media, and restricted it to terrorism and drug-related cases.
Parliamentary speaker Fathi Sorour said all detainees arrested under the law for other offenses would be released starting June 1, when the amendments go into effect.
Cases involving insults against religions have been previously referred to the emergency courts' state security prosecution.
Yusef Zeidan, the Muslim author of the acclaimed novel "Azazil," which angered the Coptic Church, said earlier this month that state security prosecution wanted to question him for insulting Christianity.
Hani Nazeer, a Coptic blogger, has been detained under the emergency law since 2008 after a posting on his blog linked to a website considered insulting to Islam. The law allows for indefinite detentions.
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