The annual report by Reporters Without Borders (RSF) said Tuesday that journalism was at least partly blocked in nearly three-quarters of the 180 countries surveyed.
Its World Press Freedom Index found 73 countries "totally blocked or seriously impeded" journalism, while it was "constrained" in 59 others, adding that many governments had used the pandemic to worsen repression.
"Journalism is the best vaccine against disinformation," RSF secretary-general Christophe Deloire said in a statement.
"Unfortunately, its production and distribution are too often blocked by political, economic, technological and, sometimes, even cultural factors."
Eritrea, North Korea, Turkmenistan, China, and Djibouti fared worst overall in this year's RSF ranking.
Norway, Finland, Sweden, Denmark, and Costa Rica were ranked highest.
The Middle East and North Africa region continue to be the most repressive for journalists, the report found, highlighting the worsening situation in Iran, Saudi Arabia, Egypt, and Syria over the past year.
"In this region, still the toughest and most dangerous for journalists, the pandemic has exacerbated the problems that have long plagued the press, which was already in its death throes," it said.
Malaysia recorded the worst deterioration, down 18 places in the ranking to 119, due in part to a recent "anti-fake news" law "allowing the government to impose its own version of the truth".
RSF said the global level of media freedom remained largely stable overall for the past year, but noted that the figures had deteriorated by 12 percent since the ranking was first launched in 2013.
Part of the problem is falling trust in journalists, fuelled by political polarisation and online misinformation.
RSF noted a recent survey by the Edelman Trust that found 59 percent of respondents across 28 countries believed journalists deliberately misled the public.
The World Press Freedom Index is based on questionnaires sent to experts around the world, combined with data on abuse and acts of violence against journalists to form a picture that includes pluralism, media independence, self-censorship and other factors.