By Saskya Vandoorne and James Griffiths, CNN

(CNN) -- Maria Ressa, the CEO of the Philippine news website Rappler, said Monday that her reporters would not be silenced in the face of tax evasion charges, telling CNN that "journalists are more important today than ever."

Ressa vowed to fight the charges from the Philippines Department of Justice for tax evasion, which many see as a thinly veiled attempt by President Rodrigo Duterte to muzzle the investigative news site.

"In many ways the government's attacks against Rappler have made it very clear to us exactly who we are, what our identity is, and for our young reporters who are on the ground, how clear and necessary our mission is today," Ressa told CNN's Kristie Lu Stout from Paris, where she is in town for a peace forum.

"Our democracy is in transition," said Ressa, a former CNN bureau chief and award-winning journalist. "The mission of journalism has never been needed as much as it is now, and we'll continue doing these stories."

'Fearless reporting' under fire

Rappler has been a consistent thorn in the side of the Duterte administration, closely documenting its so-called "war on drugs," a widespread crackdown that has been condemned for encouraging thousands of extrajudicial killings.

In January, the Philippines Securities and Exchange Commission (SEC) temporarily revoked Rappler's registration on the basis that it had violated the country's constitution over foreign ownership rules.

This month, officials said Rappler and Ressa failed to declare about $3 million in 2015 on tax returns from an investment by the Omidyar Network, a fund created by eBay founder Pierre Omidyar.

On Friday, the country's Justice Department said it had "found probable cause" to indict Rappler and Ressa on charges of tax evasion.

The company said it was not surprised by the move, "considering how the Duterte administration has been treating Rappler for its independent and fearless reporting."

Ressa told CNN that the cases leveled against Rappler were "because we are trying to fight impunity on two fronts." She said the first front was "the drug war." And the second front, she said, was "lies on social media" that are "actually the basis of many of the cases that were filed against us by the government."

Duterte's office has denied he is involved in the prosecutions against Rappler, but the President has previously sparred with the company's employees, personally barring Ressa and reporter Pia Ranada from Malacañang Palace, his official residence, over their coverage of his administration.

In a statement Monday, Duterte spokesman Salvador S. Panelo said the case was about whether Rappler "violated the law."

"The Department of Justice has found probable cause, hence a case was filed against the media outlet," he said. "If you violate the law, then you can not escape the wrath of its punishment ... the law may be harsh but it is the law."

Duterte and Trump reading from 'same playbook'

Ressa said there were many similarities between Duterte and US President Donald Trump's approaches to the press, telling CNN that the leaders were reading from "the same playbook."

"When President Trump called CNN and the New York Times 'fake news,' a week later President Duterte called Rappler 'fake news,'" said Ressa.

Ressa added that the "seeding of lies on social media" was leading to "authoritarian-style leaders using their power to push back against our old gate-keeping powers."

In the latest Press Freedom Index, the Philippines fell six places to 134th of 180 countries, with the report's authors warning that the "dynamism of the media has ... been checked by the emergence of a leader who wants to show he is all powerful."

Duterte aside, Rappler has attracted widespread praise for its coverage. Last week, Ressa was in the US to accept a Knight International Journalism Award from the International Committee for Journalists (ICFJ).

In a statement announcing the award, the ICFJ lauded Ressa as an "intrepid editor and media innovator who holds a spotlight to the Philippine government's bloody war on drugs."