UNITED NATIONS — A scandal about the sexual abuse of Congolese women and children by U.N. officials and peacekeepers intensified yesterday with the broadcast of explicit pictures of a French U.N. worker and Congolese girls and his claim that there was a network of pedophiles at the U.N. mission in the Congo.

ABC News' "20/20" program showed pictures taken from the computer hard drive of a French U.N. transport worker that reportedly contained thousands of photos of him with hundreds of girls. In one frame, a tear can be seen rolling down the cheek of a victim.

The report coincided with the United Nation's new Congo-wide "zero-contact" rule banning any interaction between U.N. soldiers and locals.

The staffer, Didier Bourguet, 41, is facing charges of sexual abuse and rape in France. His lawyer, Claude de Boosere-Lepidi, said in court last week that there was a network of U.N. personnel who had sex with underage girls and that Bourguet had engaged in similar activity in a previous U.N. posting in the Central African Republic.

Bourguet's case is the only one that has been prosecuted among 150 allegations against some 50 soldiers and U.N. civilian officials who have served in the Congo's peacekeeping mission. At least seven cases of sexual exploitation and abuse have been documented against peacekeepers based in Bunia, a northeastern town. One civilian has been suspended until the probe is complete, and another has resigned from the United Nations. The organization is conducting further investigations and expects more cases to come up.

Secretary-General Kofi Annan sent a letter to the Security Council on Wednesday announcing a set of strict new measures designed to stem the sexual abuse that has haunted peacekeeping operations for decades. The Democratic Republic of Congo hosts the United Nation's largest peacekeeping mission, with 13,950 soldiers and 1,875 civilian employees — and thus the greatest potential for problems.

Peacekeepers are no longer allowed to have contact with Congolese except to carry out their official duties and cannot even buy fruit from vendors; they must wear their uniforms even when off-duty or off their base. A general curfew has been imposed from 6 p.m. to 6 a.m., and bars and some cafes are designated off limits to U.N. soldiers and civilians. Offenders will be repatriated.

"We cannot tolerate even one instance of a United Nations peacekeeper victimizing the most vulnerable among us," Annan's letter said, adding that the sexual abuse does "great harm" to the tradition and honor of U.N. peacekeeping and the reputations of the countries that supply troops. "Most important, however, such behavior violates the fundamental 'duty of care' that United Nations peacekeepers owe to the very peoples they are sent to protect and serve."

The harsh new measures also illuminate how difficult the problem has been to solve and the challenges ahead.

A report by U.N. investigators last summer noted that there had been "zero compliance" with the "zero-tolerance" policy instituted in October 2003, and that peacekeepers had traded favors with colleagues to withhold reports of policy violations.

The United Nations has no power to prosecute peacekeepers or civilians. The organization can only repatriate individuals and waive their immunity so they can face trial at home. Whether they are punished depends largely on the politics and culture of their country, and U.N. officials admit that they have been historically lax on following up cases.