More than 2 million people have been displaced by the ongoing conflict in Sudan, according to the United Nations.

The numbers were revealed as one U.N. official warned that escalating attacks in Darfur could amount to "crimes against humanity."

Sudan has plunged into chaos since mid-April when monthslong tensions between the military and its rival, the paramilitary Rapid Support Forces, exploded into open fighting in the capital, Khartoum, and elsewhere across the northeastern African nation.

The fighting continued unabated Wednesday in parts of the capital and the western region of Darfur, both have seen some of the worst battles. At least 959 civilians have been killed and about 4,750 others were wounded as of June 12, according to Sudan’s Doctors Syndicate, which tracks civilian casualties.

The brutal clashes have forced more than 1.6 million people to leave their homes for safer areas inside Sudan, according to the International Organization for Migration. About 530,000 others fled to the neighboring countries of Egypt, South Sudan, Chad, Ethiopia, the Central African Republic, and Libya, the agency said.

The medical group said the toll could be much higher, given it was unable to take into account those who were killed or wounded in the ongoing clashes in Genena, the provincial capital of West Darfur. The city’s hospitals have been out of service since the fighting erupted there in April, the group said.

All of Sudan’s 18 provinces experienced displacement, with Khartoum at the top of the list with around 65% of the total number of displaced people, followed by West Darfur with over 17%, according to the IOM’s Displacement Tracking Matrix.

In Genena, the provincial capital of West Darfur, the RSF and allied Arab militias rampaged through the city over the past week, killing and wounding hundreds of people, according to local activists and U.N. officials.

Activists and residents in Genena reported dozens of women were sexually attacked inside their homes and while trying to flee the fighting. Almost all rape cases were blamed on the RSF, which didn’t respond to repeated requests for comment.

Khamis Abdalla Abkar, the provincial governor of West Darfur province, accused the RSF and allied militias of attacking local communities across Genena. In a phone interview on Wednesday with Saudi-owned television station, Al-Hadath, he urged the international community to intervene to protect civilians in his province.

Hours after his interview with the television station, Abkar was abducted and killed, said Mini Arko Minawi, the governor of the Darfur region. The circumstances of Abkar's abduction and killing were not immediately clear.

A video footage circulating on social media late Wednesday showed a group of armed men, some wearing RSF uniforms, detaining Abkar. Another night footage – too graphic to broadcast – purportedly showed Abkar laying on the ground with wounds in his neck and face. Sounds of gunfire were heard as well as people shouting in Arabic, "This is the governor," and "God is great."

Volker Perthes, the U.N. envoy in Sudan, said Tuesday the fighting in Genena has taken "an ethnic dimension," with Arab militias and armed men in RSF uniforms showing "an emerging pattern of large-scale targeted attacks against civilians based on their ethnic identities."

Such attacks, "if verified, could amount to crimes against humanity," he warned.

Alice Wairimu Nderitu, the U.N. special adviser on the prevention of genocide, also condemned "the shocking violence" in Genena. She warned in a statement Tuesday that such fighting could turn into "renewed campaigns of rape, murder, and ethnic cleansing amounting to atrocity crimes."

Darfur had been the scene of genocidal war in the early 2000s, when ethnic Africans rebelled, accusing the Arab-dominated government in Khartoum of discrimination. Former dictator Omar al-Bashir’s government was accused of retaliating by arming local nomadic Arab tribes, known as Janjaweed, who targeted civilians.

The Janjaweed later evolved into the RSF.