BAGHDAD (Reuters) - U.N. Secretary General Ban Ki-moon said on Monday he was concerned about alleged abuses by Iraqi pro-government forces in their war against Islamic State and called for investigations into any wrongdoing.
Ban's remarks, made during a one-day visit to Iraq, amounted to the strongest warning to date by a world leader regarding the suspected conduct of some of the Shi'ite paramilitaries battling Sunni Muslim Islamic State fighters.
Speaking alongside Iraqi Prime Minister Haidar al-Abadi, Ban called for the different "volunteer armed groups" -- a broad term referring to Shi'ite paramilitary factions -- to be brought under government control.
"I am ... concerned by allegations of summary killings, abductions and destruction of property perpetrated by forces and militias fighting alongside Iraqi armed forces," Ban said after meeting Iraqi officials.
"Alleged violations or abuses of human rights must be investigated and perpetrators need to be held to account."
Ban said actions committed by Islamic State against Iraq's Shi'ite majority and religious minorities, including massacres of soldiers and executions of civilians, did not justify any similar action by the pro-government fighters.
"Civilians freed from the brutality of Daesh should not have to then fear their liberators," Ban said, using the Arabic acronym for Islamic State.
"One form of violence cannot replace another," he added, alluding to reports of abuse against ordinary Sunnis when their areas were freed from Islamic State.
The Shi'ite armed factions, who have been leading the fight against Sunni jihadists since the near collapse of the Iraqi army last summer, have denied accusations of abuse.
Islamic State, which wishes to erect a medieval-style caliphate across the Middle East, seized nearly all of Iraq's Sunni territories in 2014.
Ban told reporters he was concerned that neither Baghdad nor international organisations could take care of the more than 2.5 million Iraqis displaced by the continuing conflict.
"The threat of additional and secondary displacement during ongoing military operations may overwhelm local and international capacities," he said.
Abadi, who spoke before Ban, said anyone who committed human rights violations should be brought to court.
A moderate Shi'ite Islamist, Abadi came to power after Islamic State's military rise last summer. He said that, while the majority of crimes were carried out by Islamic State, some abuses had been committed by those fighting the Sunni jihadists.
He said most of those cases had happened last summer as Islamic State swept across central Iraq, and people feared for their lives. "Our commitment to human rights is final and definite," Abadi said.
Sunni civilians complain rights abuses continue to the present day.
After his visit to Iraq, Ban is due to travel to Kuwait for a conference on Syrian refugees.
(Reporting by Ned Parker; Editing by Crispian Balmer)