Egyptian secret police have arrested an award-winning Australian journalist and an Egyptian reporter for the Qatar-based Al-Jazeera channel on suspicion of illegally broadcasting news harming "domestic security", the interior ministry said.
Al-Jazeera confirmed the arrests in a statement and said police also detained a producer and a cameraman.
Officers of the National Security service raided their makeshift bureau at a Cairo hotel on Sunday, arresting two of the journalists and confiscating their equipment, the ministry said in a statement.
It did not identify the journalists, only mentioning that one was a "Muslim Brotherhood member" and the other an Australian.
Al-Jazeera English identified them as Cairo bureau chief Mohamed Adel Fahmy and Australian reporter Peter Greste.
It said producer Baher Mohamed and cameraman Mohamed Fawzi were also arrested on Sunday evening.
The raid came after authorities listed the Muslim Brotherhood movement of deposed president Mohamed Morsi as a "terrorist organisation", making membership in Islamist group or even possession of its literature a crime.
The journalists "broadcast live news harming domestic security," the interior ministry said, adding they were also found in possession of Muslim Brotherhood "publications".
Greste, a former BBC journalist, won the prestigious Peabody award in 2011 for a documentary on Somalia. Fahmy, who formerly worked with CNN, is a well-known journalist in Cairo with no known links to the Brotherhood.
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Egypt's military-installed government cracked down on Al-Jazeera's affiliates following the overthrow of Morsi in July, accusing the broadcaster of pro-Brotherhood coverage.
Several Al-Jazeera reporters remain in detention, including Abdullah Elshamy, a journalist for the Arab language station arrested on August 14 when police dispersed an Islamist protest camp in Cairo, killing hundreds in clashes.
The government declared the Brotherhood a terrorist organisation last week after a suicide car bombing of a police headquarters killed 15 people.
It blamed the attack on the Islamists, although an Al-Qaeda-inspired group claimed responsibility for the bombing and the Brotherhood condemned it.
Media watchdog the Committee to Protect Journalists (CPJ) said in a report that Egypt came third for the number of journalists killed on the job in 2013, after Syria and Iraq.
"Amid stark political polarisation and related street violence, things deteriorated dramatically for journalists in Egypt, where six journalists were killed for their work in 2013," the CPJ said.
Three were killed on August 14 as they were reporting on a police crackdown on Morsi's supporters in Cairo.
It said that since 1992 it has documented the deaths of 10 journalists for their work in Egypt -- nine of them since the uprising against Hosni Mubarak erupted in 2011.