General Abdul Rashid Dostum, shown here at his palace in Shiberghan in northern Afghanistan on August 19, 2009, is a thorn in the side of President Ashraf Ghani. Photo: Reuters/Caren Firouz

Afghanistan has launched an investigation into allegations that the country’s vice president sexually assaulted a rival, in the face of mounting criticism from Western allies and activists over a pervasive culture of impunity.

Abdul Rashid Dostum, a former warlord who has a catalog of war crimes attached to his name, is accused of abducting Ahmad Ishchi last month during a traditional game of Buzkashi, or polo with an animal carcass, in northern Jowzjan province.

Dostum allegedly kept Ishchi hostage in his private compound for five days, where he was said to be tortured and sodomized.

“The attorney general’s office has begun its impartial and transparent investigation regarding the incident,” Afghanistan’s top prosecutor said in a statement late on Saturday. “The investigation will be carried out neutrally and independently.”

Officials are scrambling to gather evidence after the United States, European Union, Australia and Canada on Tuesday joined the chorus of calls for a thorough probe.

Dostum has denied the allegations, but his office said he would cooperate with any investigation. It added, however, that it prefers to “resolve” the matter by the traditional mediation of tribal elders rather than through conventional courts.

Observers are skeptical the government will sack or bring charges against Dostum, who has survived all previous allegations of abuse.

“He is too powerful to be sacked or tried in court,” said Kabul-based analyst Ahmad Saeedi.

Despite his human rights record, Dostum was invited to join the National Unity Government in 2014 in a bid by President Ashraf Ghani to attract the support of his mostly ethnic Uzbek constituency.