(Adds lawyer's arrest)
By Amina Ismail
CAIRO, Sept 29 (Reuters) - A prominent Egyptian activist who was released on probation in March was arrested again on Sunday, his family and a security source said, part of what government critics say is the largest wave of arrests since President Abdel Fattah al-Sisi took power.
Rights groups say about 1,900 people have been detained since anti-government protests began in Cairo and other Egyptian cities last week. The public prosecutor's office said on Thursday no more than 1,000 suspects had been questioned.
Alaa Abdel Fattah, a blogger and software engineer, was released in March after serving a five-year sentence for protesting without permission in breach of a 2013 law that rights groups say effectively bans protests.
Under the terms of his release, Abdel Fattah was required to spend his nights at a police station for five years. His family said he was rearrested on Sunday morning as he was preparing to leave the station.
"I arrived at the police station and I found the place where he spends the probation empty, I asked them where Alaa was ... The chief detective came out and told me that Alaa is at the national security prosecution," his sister Mona said.
The Interior Ministry could not immediately be reached for comment, but a security source told Reuters an arrest warrant had been issued against Abdel Fattah over accusations of publishing false news and inciting people to protest.
Abdel Fattah was a leading voice among the liberal youth who initially led the 2011 uprising that ended the 30-year rule of autocrat Hosni Mubarak.
Mohamed al-Baqer, a lawyer representing Abdel Fattah, was arrested late on Sunday while waiting for the interrogation of his client to start at the national security prosecutor's office, said another lawyer, Amr Imam, who witnessed the incident.
"This is a blatant violation against lawyers.. Lawyers are immune while working, just like judges and prosecutors. As a lawyer, I am afraid about getting arrested right now," he added.
Rights groups say the crackdown by Sisi's government on dissent is the most severe crackdown in recent memory. The president's backers say the authorities need to stabilise Egypt after the turmoil following the 2011 uprising.
Several hundred of those detained in the past week, including writers, activists and opposition figures, have been placed under investigation on allegations of using social media to spread false news, joining a banned terrorist group and protesting without a permit, defence lawyers say.
The United Nations High Commissioner for Human Rights, Michelle Bachelet, expressed concern on Friday over the human rights situation in Egypt.
"I remind the Egyptian government that under international law people have a right to protest peacefully," Bachelet said, adding they had a right to express opinions on social media.
"They should never be detained, let alone charged with serious offences, simply for exercising those rights," she said.
Egypt's Foreign Ministry dismissed the U.N. statement, saying it was "based on baseless information".
(Reporting by Amina Ismail; Additional reporting by Ahmed Mohamed Hassan and Omar Fahmy; Editing by Edmund Blair and Gareth Jones)
Our Standards: The Thomson Reuters Trust Principles.