The government has launched a massive crackdown
The Paris-based Reporters Without Borders (RSF) said in a report released on Wednesday that journalists had paid a "high price" since the government declared a state of emergency in November.
The report said at least 100 journalists had been arrested and at least 30 were still behind bars.
The rights group said it had confirmed that at least three journalists had been tortured.
The government declared the state of emergency two days after Maoist rebels broke a four-month ceasefire in their armed campaign to topple the constitutional monarchy.
International pressure
Amid mounting pressure on its rights record, the government released two journalists and two human rights activists from detention on Tuesday.
All four had been arrested for allegedly supporting Maoist rebels.
One of the journalists, Gopal Budhathoki, was detained for allegedly trying to demoralise the army with his articles.
The government of Prime Minister Sher Bahadur Deuba launched a massive nationwide crackdown after rebels launched their biggest attack yet in November.
And according to the RSF report, the media has become a prime target.
"The troops do as they please," rights activist Subodh Raj Pyakurel was quoted as saying.
"They completely violate the laws by arresting, questioning, torturing and detaining suspects, especially journalists," he said.
Restricted access
The report said dozens of journalists had been arrested in areas affected by the conflict and ordered under interrogation to reveal the names of any contacts they might have among the rebles.
Access to conflicts zones had also been restricted.
About 3,000 people have died since the Maoists launched their insurgency six years ago.
But the report said accurate casualties figures were increasingly difficult to come by.
It said that half a dozen publications linked to the Maoists had been closed since the state of emergency was declared.
There had also been a growing number of raids by security forces on newsrooms.
The report quoted Mr Deuba as saying the crackdown was meant to "put an end to terrorist propaganda once and for all".
A Reporters Without Borders representative urged the prime minister to release the detained journalists.
He replied that "investigations were making progress."
"If any errors have been made, the individuals concerned will be freed and compensated," the report quoted Mr Deuba as saying.