U.N. human rights officials say Sudanese security forces that were allegedly involved in killings, sexual violence and other abuses in Darfur last year have largely gone unpunished.

The U.N. Human Rights Office, in a critical new report based on information from a joint U.N.-African Union operation in Darfur, documented 411 cases of alleged violations and abuse by all parties and said "very few" ended in arrests or investigations.

United Nations High Commissioner for Human Rights, Zeid Ra'ad Al Hussein, said the report pointed to "the systemic failure, or outright refusal, by the authorities to take human rights violations seriously."

The report released Friday denounced violations of international law including "indiscriminate" aerial bombardment of civilian areas, burning of villages and destruction of other civilian property.

It pointed to a "negligible" impact of steps by Sudan's government to reduce impunity, and listed 15 recommendations to the government such as a halt to aerial bombing, granting of access to areas of human rights incidents, and strengthening judicial impartiality. Its five recommendations for rebel groups included refraining from violence against civilians, cooperating with investigators and participating in peace initiatives.

Darfur has been in turmoil since 2003, when ethnic Africans rebelled, accusing the Arab-dominated Sudanese government of discrimination. The United Nations says 300,000 people have died in the conflict and 2.7 million have fled their homes.

The report noted an upsurge in violence after Sudanese forces deployed in Darfur in February 2014. According to the report, the joint A.U.-U.N. operation documented 127 cases of sexual, gender-based violence with more than 200 survivors, but found only 12 of those cases went to court.

Authorities have repeatedly cited a climate of impunity over Darfur. Fatou Bensouda, chief prosecutor at the International Criminal Court, has accused the Security Council of failing to respond to 10 requests from the tribunal for action against individuals that failed to cooperate, including President Omar al-Bashir, who is wanted for alleged war crimes in Darfur.