The United Nations is investigating 150 allegations of sexual abuse by peacekeepers in Congo, a disturbing sign that efforts to rid the so-called "blue helmets" of such misconduct in recent years haven't worked, officials said Monday.

The allegations include pedophilia, rape and soliciting prostitutes, said Jane Holl Lute (search), assistant secretary-general for peacekeeping operations. Similar claims have been made against peacekeepers working under the U.N. mandate in the past.

"It's important that those missions be above reproach and adhere to a standard of condition which not only we have a right to expect, but the people in these circumstances themselves have a right to expect," Lute said.

The allegations in Congo started coming to light in the spring, and formal investigations have begun in several cases, she said. There are allegedly photographs and video footage backing some of the claims.

Many of the cases came out of the eastern Congolese city of Bunia (search), where a large contingent of peacekeepers is based.

The United Nations mission in Congo has about 10,500 soldiers and police as well as 1,000 international staff from 50 countries. It began in 1999. Investigators are now checking the 15 other U.N. peacekeeping missions around the world to see how widespread the problem is, Lute said.

Allegations of sex abuse and other crimes have dogged U.N. peacekeeping missions almost since their inception in 1948. It's been difficult to clamp down because the United Nations doesn't want to offend the relatively small number of nations who provide most of its peacekeeping troops.

There is little the United Nations can do anyway, since it relies on those same governments to prosecute suspected offenders, who often return home to face light punishment — if any at all.

In recent years, the United Nations has tried to clear up sex abuse problems by putting more emphasis on training peacekeepers — known as "blue helmets" (search) for their distinctive headgear — and re-emphasizing codes of conduct.

But Lute said those efforts have not kept pace with the massive growth in peacekeeping missions, and their complexity — where soldiers often are deployed in highly volatile, lawless areas rather than manning clearly defined truce lines.

Officials have refused to give details about specific cases in Congo, but at least three civilians with the U.N. mission there have been suspended.

Lute said U.N. leaders were now determined to get tougher. On Friday, Secretary-General Kofi Annan (search) said he was "absolutely outraged" by the allegations.

So-called "personnel conduct officers" have been sent to the missions in Congo, Burundi, Ivory Coast and Haiti.

Several investigative teams have been deployed to Congo, including one that arrived Monday to pursue allegations against accused civilians. Another is on its way to study long-term proposals. The United Nations is also making the complaint process easier in countries where peacekeepers are posted.

In July, Annan named Jordan's U.N. Ambassador Prince Zeid Al Hussein (search) a special adviser on sexual exploitation with the hope that he can talk to governments and make sure they pursue claims against their soldiers.

"I'm talking to governments so we have a collective response to assist the secretary-general and the U.N. by ensuring that these cases don't arise in the future," Zeid told The Associated Press.

The United Nations hopes Zeid's background will give him the power he needs in an extremely difficult task. He is one of the few U.N. ambassadors with peacekeeping experience, in Bosnia in 1994-95. In addition, Jordan is among the top troop suppliers for U.N. missions.