Egypt's military-led authorities shut down several stations, including one operated by the Muslim Brotherhood, after President Mohamed Morsi was toppled by the army.
The security forces on Wednesday also raided the offices of Al Jazeera's Egyptian news channel and detained at least five of its staff, said Karim El-Assiuti, one of its journalists. Four of them were later released, the channel said.
The channel, Al Jazeera Mubasher Misr, was prevented from broadcasting from a pro-Morsi rally in northern Cairo and its crew there was also detained.
Al Jazeera's Egyptian station began broadcasting after the 2011 revolution that topped President Hosni Mubarak and has been accused by critics of being sympathetic to Morsi's Muslim Brotherhood.
Our correspondents reported being interrupted during a live broadcast, with presenters and guests being arrested.
Muslim Brotherhood-owned Egypt25 was also forced off air and its managers arrested shortly after General Abdel Fattah al-Sisi, head of Egypt's armed forces, announced a plan for a new political transition, the state news agency MENA reported.
The authorities also shut down two other Islamist-run stations, Al-Hafiz and Al-Nas, security sources said.
Both are affiliated to the strict Salafi Islamist movement.
"We are concerned by reports that authorities are shutting down television coverage based on political perspective," said Sherif Mansour of the New York-based Committee to Protect Journalists.
"We urge the military not to deprive Egyptians of information sources at this important juncture."
Speaking to Al Jazeera English, National Salvation Front spokesman Khaled Dawoud defended the move.
"Unfortunately these are exceptional circumstances," he said.
"I don't believe closing down any newspaper or any channel is a useful measure ... but we are going through a very critical time here, the situation is dangerous.
"I hope this is an exceptional measure that will last only for a few days, but when you have a critical time of change like this and you have some other people who are trying to incite supporters to go and fight I don't think it is useful to have these channels working at these critical hours."