Human Rights Watch (HRW) has accused the Palestinian Authority of perpetrating "blatant attacks" on free speech in the West Bank and Gaza Strip over the past two years.

The New York-based organisation documented seven cases of abuse of journalists investigating corruption in the West Bank, as well as two instances in the Hamas-run Gaza Strip.

Offences included detaining journalists for no reason, assault and intimidation. In one case a filmmaker was arrested and held in custody for 24 days, then forced to sign a confession incriminating him for being engaged in anti-government activity.

Another journalist, Khalid Amayreh, told HRW that he had been forced to sleep in a toilet as part of his punishment for criticisng Palestinian Authority suppression of protests.

HRW said the treatment was not limited to the media but was also applied to "many other citizens in the West Bank, in Gaza, who are critics or who are perceived to be critics of the government or of the authorities".

The findings followed claims by media watchdog the Committee to Protect Journalists (CPJ) that four reporters who were attempting to cover peaceful protests in Gaza were "physically assaulted and obstructed" last week.

Joe Stork, HRW's deputy Middle East director, said: "Palestinian security forces are becoming notorious for assaulting and intimidating journalists who are just trying to do their jobs.

"Both the Palestinian Authority in the West Bank and Hamas in Gaza need to end these blatant attacks on free expression."

He added: "The utter failure of the PA leadership to address the prevailing culture of impunity for such abuses suggests that they reflect government policy."