GENEVA (AP) — The violence in Syria has worsened since a cease-fire deal in April and the bloodshed appears to be taking on dangerous sectarian overtones, the U.N. said Wednesday.

Investigators say they have concluded that Syrian government troops could be behind the killing of more than 100 civilians in the village of Houla last month. The findings, which were presented to the U.N.’s top human rights body, could lay some of the groundwork for prosecuting alleged crimes against humanity or war crimes in Syria.

Reflecting the sense of urgency, senior diplomats said world powers are planning to meet Saturday in Geneva in an attempt to end the bloodshed. U.S. Secretary of State Hillary Rodham Clinton and Russian Foreign Minister Sergey Lavrov will be joined by other top diplomats from U.N. Security Council nations and possibly neighbors of Syria.

Activists say more than 14,000 people have been killed since the uprising against President Bashar Assad’s regime began in March last year.

The U.N.’s deputy envoy for Syria, Jean-Marie Guehenno, told the U.N. Human Rights Council that the violence in Syria has “reached or even surpassed” levels seen before the April 12 cease-fire agreement and that a six-point peace plan forged by his boss, U.N.-Arab League envoy Kofi Annan, “is clearly not being implemented.”

Meanwhile, a U.N. probe into the massacre in the central Syrian village of Houla concluded that forces loyal to the government “may have been responsible” for many of the deaths.

The report by U.N.-appointed human rights experts says the military or pro-government shabiha forces had better access to the Houla village during the May massacre. The village leans toward the opposition and most of the victims were women and children who were slaughtered in their homes, it said.

“The manner in which these killings took place resembles those previously and repeatedly documented to have been committed by the government,” the head of the expert team, Brazilian professor and diplomat Paulo Sergio Pinheiro, told the U.N.’s top human rights body in Geneva.

However, he said a final verdict on who was responsible for the massacre would require further investigation by his team.

In unusually forceful language, Pinheiro also said interviews conducted by the commission “indicated that government forces and shabiha have committed acts of sexual violence against men, women and children.”

The panel said it concluded that growing numbers of Syrians also are being targeted in the country’s conflict on account of their religion.

“Where previously victims were targeted on the basis of their being pro- or anti-government, the Commission of Inquiry has recorded a growing number of incidents where victims appear to have been targeted because of their religious affiliation,” said the panel’s report delivered to the Human Rights Council.

Fayssal al-Hamwi, a Syrian ambassador in Geneva, charged that the allegations against the government are “quite fantastic.” Then calling the council meeting blatantly political, he said he no longer wished to participate and strode out.

The increasing militarization of both sides in the conflict has Syria lurching toward civil war. The failure of Annan’s internationally brokered peace plan has made it more difficult for outside observers, humanitarian workers and supplies to get into Syria or for reliable information to filter out.

U.N. officials were expected to make an announcement later Wednesday on the Saturday meeting. Guehenno, a former U.N. peacekeeping chief, said the Syrian government and rebel groups must be made to understand that there are “consequences” for failing to implement the peace plan.

“But this effort cannot be open-ended. Time is running out. Syria is spiraling into deeper and more destructive violence,” he said.

Russia and China, two of the Security Council’s five permanent members, have twice shielded Syria from U.N. sanctions.