UNITED NATIONS, May 6 (Reuters) - The United Nations said on Tuesday it was disappointed by a court judgment in Democratic Republic of Congo that only convicted two Congolese soldiers over a mass rape in 2012 and acquitted another 13 officers.

The U.N. accused soldiers from two Congolese battalions of raping at least 97 women and 33 girls, some as young as 6, in the eastern town of Minova after the troops fled from advancing M23 rebels in November in 2012.

"By this judgment, the judiciary did not meet the expectations of the numerous victims of rape who fully participated in the trial," U.N. human rights spokesman Rupert Colville told reporters.

"The outcome of the trial confirms shortcomings in the administration of justice in the DRC," he said. "There is no possibility for appeal as per the rules of procedure of the Operational Military Court, in contradiction of international standards as well as the Congolese Constitution."

A military court sentenced two soldiers to life in prison over the mass rape in 2012, a lawyer for the defense, Sabra Mpoy, said on Monday. However, 13 senior officers also accused in the mass trial were acquitted for lack of evidence, he said.

Another 24 soldiers were sentenced to between 10 and 20 years in prison for looting and disobeying orders not to leave their camp near Minova during the incident, Mpoy said.

The U.N. peacekeeping mission in Congo threatened in February last year to withdraw support for two Congolese battalions accused of involvement in the mass rape.

The mission decided to keep working with the 41st and 391st battalions after 12 senior officers, including the commanders and deputy commanders, were suspended and about a dozen soldiers were charged over the rapes in Minova.