Egypt's military arrested a BBC journalist when it cleared out a central Cairo protest that left several protesters injured and dozens detained, officials with the British broadcaster said on Tuesday.
Shaimaa Khalil was detained on Monday after the military, backed by riot police, cleared the three-week sit-in in Tahrir Square, they said.
The BBC's foreign editor John Williams wrote on his Twitter account that the broadcaster was trying to secure her release.
"Very concerned at the detention of Shaimaa Khalil in Cairo -- a good journalist doing her job. Doing all we can to secure her release," he wrote.
Khalil had been posting updates on Twitter before her arrest.
""Careful!' someone just told me. 'They arrest anyone taking photos," she wrote.
Witnesses said soldiers and police beat demonstrators and broke mobile phones, targeting anyone taking pictures.
Here is what she wrote on her Twitter feed. Read it from the bottom up. The links to photos work. (Latest tweet indicates she is OK.)
Shaimaakhalil shaimaa khalil
#Tahrir now ... surrounded by military , riot police and armoured vehicles..extremely tense #TwitPict http://twitpic.com/5zgqet
Shaimaakhalil shaimaa khalil
Shaimaakhalil shaimaa khalil
#Tahrir main ring now.. "careful!" someone just told me.. "they arrest anyone taking photos " #TwitPict http://twitpic.com/5zgkkv
Shaimaakhalil shaimaa khalil
Shaimaakhalil shaimaa khalil
#jan25 monument taken apart and lifted on a truck ... #Tahrir now#TwitPict http://twitpic.com/5zgiz4
Shaimaakhalil shaimaa khalil
#Tahrir now ... military and riot police in control of the square forbidding any gathering #TwitPict http://twitpic.com/5zghaw
Shaimaakhalil shaimaa khalil
Shaimaakhalil shaimaa khalil
#Tahrir now military police everywhere "there was no resistance"1 of them tells me."we came in boom!" #TwitPicthttp://twitpic.com/5zga5v
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Shaimaakhalil shaimaa khalil
#Tahrir now armoured vehicles , police cars and traffic back to normal #TwitPict http://twitpic.com/5zg8j1