Dec 10 (Reuters) - December 10 marks Human Rights Day, the 65th anniversary of the landmark Universal Declaration of Human Rights (UDHR), signed by 48 nations - with just eight abstentions.

Sixty-five years ago, naysayers insisted it was nobody else's business how governments behaved within their borders. The declaration confronted this cynical view - and continues to do so today. Human rights abuses and their consequences spill beyond national borders, darkening prospects for harmony and stability across the globe. Freedom of religion or belief, as well as other human rights, are essential to peace and security. They are everyone's business.

Each signatory nation pledged to honor and protect these rights. For example, the declaration provides the foundation for much of the agenda of the U.S. Commission on International Religious Freedom, on which we serve.

Yet 75 percent of the world's population now lives in countries in which this freedom is highly restricted, according to a recent Pew study.

These include countries like Saudi Arabia, which abstained, as well as many that signed the declaration, including China, Iran and Nigeria.

Saudi Arabia originally refused to endorse the declaration, in part because of its ban on all public religious expression besides its own extreme interpretation of Sunni Islam. The Kingdom not only continues on this path, but has exported its religious ideology to other nations, fueling religious freedom abuses, including violence. To grasp the security implications of this approach, Americans need only recall that 15 of the 19 attackers on September 11 were Saudi nationals,.

All but one of the other abstaining nations comprised the old Soviet Union or its satellites, long notorious violators of religious liberty and other human rights. Today, Russia continues to engage in serious abuses, as Moscow passes extremism laws against certain Muslim groups and "non-traditional" religious communities, particularly Jehovah's Witnesses. The government orchestrates raids, detains and imprisons people who practice these religions. Mass human rights violations also continue in the North Caucasus region.

Another serious problem, however, are nations that signed the declaration but continue to abuse religious freedom.

In China, the government is persecuting Tibetan Buddhists and Uighur Muslims. Beijing is repressing and arresting leaders as well as members of independent Catholic and Protestant churches, shuttering their places of worship and imposing long prison sentences. It is also perpetrating forced renunciations and acts of torture on members of the Falun Gong and other groups deemed "evil cults."

In Myanmar, the military government's celebrated political reforms have yet to improve religious freedom. Sectarian violence continues with impunity against ethnic minority Christians and Muslims. The plight of the persecuted Rohingya Muslims, for example, is a tragedy.

Egypt, another signatory, also has a history of repressing religious minorities, which continued during the administrations of both Hosni Mubarak and Mohamed Morsi. Cairo did not protect Coptic Christians from violence, while prosecuting and jailing Christians and others for "defamation" of religion.

Iran also continues to detain, torture and even kill members of religious minority groups, including Baha'is and Christians, whose beliefs are viewed as a fundamental threat to the theocratic state and its interpretation of Shi'ite Islam. It is still using terrorism to export its extremism.

The Nigerian government, another signatory, has failed to bring to justice the perpetrators of sectarian violence between Muslims and Christians, which has claimed the lives of more than 14,000 Nigerians since 1999. It has not countered the Islamist terrorist group, Boko Haram, which also fuels sectarian fires.

Pakistan is another signatory facing a rise in sectarian violence. Religious liberty abuses have increased to unprecedented levels. Sunni extremists are targeting religious minorities, including Shi'ites, Christians and Ahmadis. Pakistan's government helps fuel the bloodshed through its anti-blasphemy laws, which foster vigilante violence against perceived transgressors.

These countries have not only betrayed the commitment made in 1948; they have done nothing to advance peace and security within or beyond their borders.

Indeed, study after study confirms that countries that do not protect freedom of conscience produce strife and instability, including terrorism.

The United States and the entire world community have an enormous stake in upholding the UDHR's human rights principles - including religious freedom. On this Human Rights Day, it is time to reaffirm the declaration by holding its signatories accountable.

(Katrina Lantos Swett and Mary Ann Glenndon)

(Katrina Lantos Swett serves as vice chairwoman of the U.S. Commission on International Religious Freedom. Mary Ann Glendon serves as a commissioner of the group. The opinions expressed are their own.)