High-profile Philippine journalist Maria Ressa was convicted Monday in a cyber libel case that press freedom advocates have branded a ploy to silence critics of President Rodrigo Duterte.

Ressa, 56, and her news site Rappler have been the target of legal action and probes after publishing stories critical of Duterte's policies, including his drug war that has killed thousands.

She was allowed to remain free on bail after the verdict pending a possible appeal of the conviction, which carried a sentence of up to six years.

"We are going to stand up against any kind of attacks against press freedom," Ressa told journalists after the conviction in Manila.

Monday's verdict decided a trial that stemmed from a businessman's 2017 complaint over a Rappler story five years earlier about his alleged ties to a then-judge on the nation's top court.

Ressa, who Time magazine named as a Person of the Year in 2018, did not write the article and government investigators initially dismissed the businessman's allegation.

But state prosecutors later filed charges against her and Reynaldo Santos, the former Rappler journalist who wrote it, under a controversial cyber crime statute aimed at online offences such as stalking and child pornography.

The law they are accused of violating took effect in September 2012, months after the article was published.

But prosecutors say Rappler's typographical correction to the story in 2014 to change "evation" to "evasion" was a substantial modification and the article was thus covered by the law.

High-profile Philippine journalist Maria Ressa says she could be jailed for up to seven years
High-profile Philippine journalist Maria Ressa says she could be jailed for up to seven years AFP / Ted ALJIBE

"I've been the cautionary tale: be quiet or you're next... that's part of the reason why I have been targeted," Ressa, a co-founder of Rappler and a former CNN journalist, told AFP in an exclusive interview last week.

Duterte's government has said the case is not politically motivated and that authorities must enforce the law, even against journalists.

But rights groups and press advocates say the libel charge along with a series of tax cases against Rappler and a government move to strip the news site of its licence amount to state harassment.

Amnesty International said the "attacks" against Rappler were part of a wider government crackdown on media freedom in the Philippines.

Ressa's verdict comes just over a month after government regulators forced off the air ABS-CBN, the nation's top broadcaster, following years of threats by Duterte to shut down the network.

Both Rappler and ABS-CBN have reported extensively on Duterte's anti-drugs campaign in which police have gunned down alleged dealers and users in operations condemned by rights groups.

Some of the crackdown's highest-profile critics have wound up behind bars, including Senator Leila de Lima, who is serving three years in jail on drug charges she insists were fabricated to silence her.

In 2018, Duterte denounced Rappler as a "fake news outlet" and subsequently banned Ressa and her colleagues from his public engagements.