Amnesty International is accusing U.N. peacekeepers of indiscriminately killing a 16-year-old boy and his father, and raping a 12-year-old girl in separate incidents in Central African Republic, the latest in a series of allegations of misconduct against peacekeepers in the country.

U.N. Secretary-General Ban Ki-moon is "personally dismayed and disappointed," his spokesman Stephane Dujarric said Tuesday. "We would like to emphasize once more that no misconduct of this nature will be tolerated."

The U.N., however, has no powers of criminal investigation or prosecution, leaving it up to peacekeepers' home countries — which U.N. officials often don't name publicly.

Amnesty International said the two incidents on Aug. 2 and 3 occurred as the peacekeepers from Rwanda and Cameroon were carrying out an operation in tCentral African Republic's capital, Bangui. U.N. peacekeepers have been in the country since September to try to calm unprecedented, deadly violence between Christians and Muslims.

The girl was hiding in a bathroom when a man wearing a U.N. peacekeeping helmet and vest "took her outside and raped her behind a truck," a statement from the human rights group said. It said a nurse who examined the girl "found medical evidence consistent with sexual assault."

The next day, after armed clashes with residents had killed a soldier from Cameroon and wounded several others, peacekeepers went to the area and "began shooting indiscriminately in the street where the killings had taken place," the group said.

Amnesty International said resident Balla Hadji, 61, and his son Souleimane Hadji, 16, were shot and killed outside their home. The group said it interviewed 15 witnesses immediately after both incidents, plus the 12-year-old girl and her family.

"An independent civilian investigation must be urgently launched, and those implicated must be suspended immediately and for the duration of the investigation," the organization's senior crisis response adviser, Joanne Mariner, said.

But one week after the U.N. was first informed of the allegations, it was not clear just how the peacekeeping mission in Central African Republic was looking into them. The U.N. peacekeeping office in New York wasn't informed until Monday, despite its recent order to all peacekeeping missions to immediately tell it about any such allegations.

The U.N. mission, known by its French acronym of MINUSCA, said through its spokesman Hamadoun Toure that it was "not aware" of the allegations but was taking the matter "very seriously."

Toure told The Associated Press that "personally, I don't think" the rape occurred. He said the peacekeepers had been trying to execute an arrest warrant for local judicial authorities when they were attacked, and that the girl was the sister of the suspect they were trying to arrest.

"I don't know how we can reach out to this girl. They won't accept any contact," said Toure. He said the mission doesn't have the names or details of the accused peacekeepers.

In an email from Bangui, the Amnesty International researcher in Central African Republic, Jonathan Pedneault, told The Associated Press that the peacekeeping mission's human rights division has "sadly, due to their own security constraints," not yet been able to investigate at the scene.

He said an international medical organization has been following the girl but that UNICEF has not yet been able to visit her family.

The U.N. has been under international scrutiny over its handling of allegations of child sexual abuse by French soldiers in Central African Republic last year, and an independent panel is now looking into that case.

As of the end of June, six allegations of sexual abuse and exploitation by peacekeepers had been reported since their arrival last fall, according to U.N. Conduct and Discipline reports.

Wire services