At least 150 women, some of them pregnant, have been executed by Islamic State fighters in the western Iraqi province of Al-Anbar, according to the Anadolu news agency.
Iraq's Ministry of Human Rights released a statement saying: "At least 150 females, including pregnant women, were executed in Fallujah by a militant named Abu Anas Al-Libi after they refused to accept jihad marriage.
"Many families were also forced to migrate from the province's northern town of Al-Wafa after hundreds of residents received death threats."
The ministry said many children died when their families were stranded in the desert after leaving their homes.
The statement says that the Islamic State fighters carried out the murders in Fallujah, the scene of fierce fighting in the second Iraq War, and that the victims were buried in mass graves.
The region is under the control of Islamic State, which has launched vicious purges against Christian and Yazidi minorities. Its fighters regard themselves as entitled to use captured women as sex slaves.