The global news agency AFP protested to the Jordanian government about a climate of intimidation against its staff on Thursday after a gang broke into its Amman office and destroyed equipment.
Separately, the French Foreign Ministry expressed its concern over the incident and warned states of their duty to protect press freedom.
Emmanuel Hoog, chairman and chief executive of the Paris-based AFP, wrote to Jordanian Prime Minister Maaruf Bakhit to complain about Wednesday's attack, which followed criticism of AFP by Jordan's state media.
On Monday, AFP was among several international media outlets to report that part of King Abdullah II's motorcade had been pelted with stones and bottles by a group of protesters during a visit to the town of Tafileh.
Jordanian officials deny the report, while AFP and its bureau chief Randa Habib were criticised by state media and by a 300-strong crowd that massed in front of the agency's office Tuesday in the normally tightly-policed capital.
On Wednesday, shortly after Habib received a threatening telephone call, 10 men armed with sticks stormed the office. An AFP journalist escaped through a side door while the gang smashed computers and destroyed files.
"Such behaviour is totally incomprehensible in a country that claims to follow the rule of law. These acts of physical and verbal violence have a serious impact on the work of journalists and therefore impact on freedom of expression and information," Hoog wrote.
"We take note of the moves that you have ordered to protect our staff and the premises as well as your condemnation of the attack. I now expect these measures to be implemented immediately and in a concrete fashion."
Hoog criticised accusations of "subversive intrigue" levelled at AFP "on the grounds that it reported, as its duty to inform obliges it to do, events that were considered negative for the image of the country and its leaders." He also addressed the "verbal threats" made to Habib.
A spokesman for the French Foreign Ministry, Bernard Valero, said Paris is "concerned by the violent aggression" aimed at AFP in Jordan, and took note of the Jordanian government's vow to investigate the attack.
Other international media organisations carried reports of Monday's incident. They were vigorously denied by the palace, government officials and lawmakers from the city.
Since January, Jordan's government has faced a protest movement demanding political and economic reforms and an end to corruption.