New York  - The United Nations marked World Press Freedom Day Thursday, using the occasion to reiterate support for the work of journalists worldwide and denounce governments that use secrecy laws to suppress freedom of the press and expression.

At a ceremony marking the occasion organized by the UN Department of Public Information headed by UN Undersecretary General Kiyo Akasaka and the UN Educational, Scientific and Cultural Organization (UNESCO), government envoys and UN officials held a minute of silence to pay tribute to journalists killed or injured while performing their duties.

UN Secretary General Ban Ki-moon reiterated UN support for press freedom and deplored violence against media representatives.

"Attacks on freedom of the press are attacks against international law, against humanity, against freedom itself - against everything the UN stands for," Ban said. "I am therefore all the more alarmed at the way the journalists are increasingly being targeted around the world, and dismayed when such crimes are not thoroughly investigated and prosecuted."

He urged "all societies to spare no efforts in bringing to justice the perpetrators of attacks on journalists."

In Geneva, the UN Commissioner for Human Rights, Louise Arbour, said media's work of informing the public about events and policies is enshrined in international human rights law.

"It's a sad fact that many governments across the world persist in undermining the freedom of the press to report facts and opinions and, by extension, the right of people in general to be informed about events and policies that are shaping our world," Arbour said, without any hints about which governments.

Arbour, a former Canadian Supreme Court justice, said those governments have increasingly resorted to their own secrecy laws and "sophisticated methods of sowing propaganda disguised as objective information" to undermine free press.

She noted how governments have cited security reasons to prevent journalists from obtaining information, a trend that has gradually resulted in undermining the principle to protect a journalists's confidential sources, which she said, constitutes a "central pillar of press freedom."

World Press Freedom Day is celebrated each year on May 3, but the event was held on Thursday because of the coming weekend. The event at UN headquarters in New York was presided over by UN General Assembly President Srjgan Kerim, who reiterated UN support for the journalists to do their work without interference and under threat of violence.

Participating in the event was the Committee to Protect Journalists (CPJ), which denounced on Wednesday a total of 13 countries - many of them democracies like Mexico and India - for failing to resolve murders of journalists.

CPJ said Iraq was on top of the Impunity Index published for the first time by the New York-based group that works to uphold freedom of the press and freedom of expression. A total of 79 cases of journalists killed since the US invasion in 2003 have remained unsolved.

The Philippines came second, with 24 unsolved killings, followed by Colombia with 20 and Russia with 14.

South Asia is particularly dangerous region for journalists, CPJ said. India, Sri Lanka, Afghanistan, Nepal, Bangladesh and Pakistan all have not solved murders of journalists.

The other countries singled out by CPJ are Sierra Leone and Somalia. (dpa)