Ressa's lawyer paid Thursday's 100,000 Filipino Pesos ($ 1,915) bail for her release after she spent the night in custody.
Following her release, the co-founder and editor of the online news magazine Rappler, who has become prominent for her tireless coverage of President Rodrigo Duterte and his brutal drug war, delivered a passionate speech on press freedom and called her case to "abuse of power and arming of the law."
"The message the government is sending is very clear: be silent or you're next," said Ressa, 2018 Time Person of the Year. "So I say, and I appeal to you, not to mention.
"Press freedom is not just about journalists, is it? It's not just about us, it's not just about me, it's not just about Rappler, press freedom is … the foundation of every single right of every Filipino to the truth so that we can hold the powerful accountable. "
Article 2012 under the magnifying glass
Ressa, who had already been bailed out on charges of tax evasion lawsuits she filed against her last November, was arrested shortly after 5:00 pm Wednesday at Rappler's Manila office.
The latest lawsuit relates a 2012 story claiming that businessman Wilfredo Keng has links to illegal drugs and human trafficking.
The article was published by Rappler two years before the entry into force of new laws against cyber-slander in the Philippines.
JJ Disini, one of Ressa's lawyers, described the charges as "politically motivated" and said that any updates made to the offending article in 2014 were "just a change in punctuation".
"If the slander had already been committed in 2012, changing the punctuation marks would not have been able to republish this slander," Disini added.
Rappler's extensive coverage of the Philippines under President Duterte has made the site – and its journalists – targets of its followers.
Ressa has been repeatedly charged with defamation and tax evasion, which critics described as politically motivated to silence independent media in the Southeast Asian country.
Anger of journalist groups
Media officials have criticized the arrest of Ressa and argued that the time gap between the alleged change in the article and its arrest indicated a political element.
"You have to wonder why the person named in this article has been waiting five years to make any charges," said Steven Butler, Asia Program Coordinator for the Committee to Protect Journalists.
"In the beginning, the Philippine government decided not to file charges, and then they changed their minds, the whole thing smells quite open, it looks like a political hack job to intimidate the press."
The National Union of Journalists of the Philippines said the arrest was "clearly a desperate move by the government to suppress the media" and a government rejection.
"This move exposes his despotic regime and his fear of accountability," the post read. "We must unite and stand for the freedom of the press in these difficult times, because Duterte systematically destroys our democracy."
The lawsuit against Ressa comes at a time when press freedom in the Philippines and around the world is being called into question.
In 2018, Ressa was named a group of journalists named Time Magazine's Person of the Year.
Other members of the group included Jamal Khashoggi, the contribution of the Washington Post, which was killed at the Saudi Arabian Consulate in Istanbul in October, and Wa Lone and Kyaw Soe Oo, two Reuters journalists arrested in Myanmar a year ago they arrested the mass killings of Rohingya Muslims.
Joshua Berlinger, Lauren Said-Moorhouse and Karen Smith of CNN contributed to the report.