GENEVA, March 20 (Reuters) - Iran's authorities have committed violations in recent months that may amount to crimes against humanity, a U.N.-appointed expert told the Human Rights Council on Monday, citing cases of murder, imprisonment, enforced disappearances, torture, rape, sexual violence and persecution.

Iran has been swept by protests since the death of a young Iranian Kurdish woman, Mahsa Amini, in custody last September.

Addressing the Geneva-based council, Javaid Rehman, Special Rapporteur on the situation of human rights in the Islamic Republic of Iran, said he had evidence that Amini died "as a result of beatings by the state morality police".

Iran's state coroner has said Amini died from pre-existing medical conditions, not blows to the head and limbs.

Rehman added that the scale and gravity of crimes committed by authorities as part of a broader crackdown against protests following her death "points to the possible commission of international crimes, notably the crimes against humanity".

He voiced outrage at the execution of at least four people linked to the protests and said that a total of 143 people had been executed in the country since January following "grossly unfair trials".

Iran's Ambassador Ali Bahreini told the Geneva-based council that the allegations were imaginary and Iran was being singled out and targeted in the council.

Reporting by Emma Farge Editing by Miranda Murray