By Syed Shoaib Hasan
BBC News, Karachi
A leading Pakistani news channel says the government is threatening to close it for its coverage of the row over the suspension of the country's top judge.
Another station, Geo TV, was attacked by police last month
Aaj (Today) says it is accused of not securing permission to broadcast and inciting violence in its reporting.
The channel denies the allegations and says it is being unfairly targeted.
Last month, police attacked the offices of another channel, Geo, for defying government attempts to influence its reporting of the crisis.
President Pervez Musharraf later apologised on air for the conduct of police, promising that the freedom of the press would be protected.
The crisis began after he suspended Chief Justice Iftikhar Mohammad Chaudhry last month, saying he had abused his position.
The judge, who has a reputation for independence, denies wrong-doing.
Observers say his suspension seems to have become a rallying point for all those with grievances against the government.
Aaj TV and Geo are currently the most popular news channels in Pakistan.
"We have done nothing wrong and have nothing to fear," Arshad Zuberi, managing director of Aaj, told the BBC News website.
Mr Chaudhry has a reputation for judicial independence
The channel is owned by the Zuberi family, who also operate the Business Recorder, Pakistan's oldest and most respected financial newspaper.
This is not the first time that the Pakistan Media Regulatory Authority (Pemra) has applied pressure or raised questions over programming.
"Previously they would raise questions over a programme and we would reply," said Mr Zuberi.
"That would be the end of the matter."
On Sunday, however, the channel was sent a legal notice asking it to explain why it had not sought permission from the appropriate government department to uplink its signals from the country.
It has also been accused of inciting violence by casting the armed forces in an unfavourable light.
The channel has been given three days to reply.
Arshad Zuberi denies all the charges.
"The recent changes in the law have made it unnecessary to get permission for up linking," he said.
As far as the other allegations are concerned, he is adamant that the channel has just been doing its job - reporting the story.
Mr Zuberi says he believes the letter was sent because of the recent coverage given by the channel to the activities of Chief Justice Chaudhry.
Pakistan's government has faced a number of recent accusations that it is trying to stifle press freedoms.
Last year, two local language channels were taken off air for a month for reporting on the insurgency by tribal militants in Balochistan province.