The Jordan Press Association said on Sunday it plans to sue the police department after several journalists were beaten up as they covered a demonstration in Amman.
"The union will file individual and collective lawsuits against the public security department," JPA president Tareq Momani said at a sit-in outside the association.
At least 17 people, including journalists and policemen, were injured on Friday when police tried to stop clashes between pro-reform demonstrators and government supporters in central Amman.
Police used batons to break up the clashes outside city hall, beating and injuring at least nine journalists wearing orange vests marked "Press."
"I apologise to journalists for agreeing with the police department to make them wear the vests. This was apparently nothing more than a trap," said Momani.
The department said on Saturday that four policemen suspected of attacking journalists had been arrested. The results of a probe would be announced within 72 hours, it said, vowing to "refer to courts those who have a case to answer."
"These police measures are not enough. There are dozens of policemen who should be held accountable," Momani said.
MPs and Islamist leaders took part in the sit-in and condemned the attacks. "I salute the journalists. What happened will not silence calls for reform," said Hamzah Mansur, head of the opposition Islamic Action Front (IAF).
Since January, Jordan has faced a protest movement demanding political and economic reforms and an end to corruption.