The U.N. and media rights groups marking World Press Freedom Day say the Arab Spring has eased the grip of some governments on journalism but many nations still use tactics to repress the media.

In a joint statement on Thursday, U.N. Secretary-General Ban Ki-moon and UNESCO leader Irina Bokova said changes in the Arab world have shown the “power for aspirations for rights when combined with new and old media.”

The Freedom House rights group says the Middle East and North Africa experienced “dramatic if precarious gains” in press freedom last year. The group cites Egypt, Libya and Tunisia for significant gains as a result of the Arab Spring. However, it says Bahrain and Syria launched “harsh media crackdowns” as part of government efforts to repress uprisings.

The group also says China, Russia and Iran kept tight grips on the media through tactics such as detaining government critics and shutting down media outlets.

Iran and Syria also fared poorly in a new report from the Committee to Protect Journalists on the “10 Most Censored Countries.” However, the group said Eritrea topped its “most censored” list because the government only allows tightly supervised state news media to operate in the country.

Reporters Without Borders marked World Press Freedom Day by condemning what it calls the “furious pace” of attacks on news providers. It says 21 journalists have been killed in 2012.

The group cited Syrian President Bashar al-Assad and Islamist militias in Somalia as the worst offenders of media freedom.

World Press Freedom Day was enacted by the U.N. General Assembly in 1993 to assess the worldwide state of media freedom and pay tribute to journalists who have died in the line of duty.