An Al Jazeera news producer has been arrested in Egypt over accusations of attempting to overthrow the government and being a member of the banned Muslim Brotherhood, Reuters news agency said quoting three security sources.
Mahmoud Hussein was arrested at his Cairo home on Friday, Al Jazeera Media Network confirmed, but it was not known where he was being held.
Al Jazeera strongly denies all accusations against Hussein.
"Al Jazeera holds Egyptian authorities responsible for the safety of Hussein and is calling for his immediate release," the Qatar-based network said in a statement.
Hussein, who lives in the capital Doha, used to work in Egypt before Al Jazeera closed its office there in 2013.
He was questioned for more than 15 hours at Cairo's airport on Tuesday after arriving for a vacation, security sources told The Associated Press news agency.
State security also stormed the homes of Hussein's two brothers and arrested them.
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Officials from the Interior Ministry were not immediately available for comment.
Egyptian authorities have over the past few years arrested several Al Jazeera employees, raising concerns over media freedom in the country.
In May, a Cairo court recommended the death penalty against Ibrahim Helal and Alaa Omar Mohamed Sablan, charging them in absentia with endangering national security.
Al Jazeera's Baher Mohamed, Mohamed Fahmy and Peter Greste - along with seven colleagues outside the country - were accused of spreading "false news" during their coverage of demonstrations against a military overthrow of then-president Mohamed Morsi in 2013, the year they went into custody.
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Baher Mohamed and Mohamed Fahmy spent 437 days in jail before being released. Greste spent more than a year in prison.
There has been a crackdown on the Muslim Brotherhood since the army takeover in 2013 stripped Morsi - a prominent member of the group - of power following mass protests against his rule.
Thousands of Brotherhood supporters, including Morsi, are in jail and Egypt has designated the group, which says it is non-violent, as a "terrorist organisation".
Source: Al Jazeera and news agencies