UN investigators said Friday they had found evidence of possible crimes against humanity by forces loyal to Ivory Coast's ex-president Laurent Gbagbo and followers of his successor Alassane Ouattara.

"The commission concluded that during the period examined, several serious violations of human rights and international humanitarian law were committed by different actors; some could constitute crimes against humanity and war crimes," said the findings of a probe ordered by the UN Human Rights Council. "These violations were committed by the Defence and Security Forces and their allies, and during their counter-offensive, and since their control of the country, by the Republican Forces of Ivory Coast," the investigators added.

The three-member inquiry panel travelled to the country from 4 to 28 May, and visited Abidjan, as well as cities including Duekoue, Guiglo, Korogho, Odienne and San Pedro.

It found that "serious crimes such as murder and rape took place through generalised and systematic attacks against the population targetted on the basis of their assumed political sympathies."

These violations included attacks by Gbagbo's forces against the population in the Abidjan suburb of Abobo, and attacks by Ouattara's forces against people of Guere origins.

War crimes may also have been committed, said the investigators, citing "acts committed in Abidjan and other cities since the end of March 2011 such as attempts on lives... cruel treatment and torture, as well as humiliating and degrading treatment" against civilians.

The investigators said they were unable to determine the death toll during the crisis which erupted after a disputed November presidential election, but on the basis of information collected on the ground, they estimate that about 3,000 people were killed.

The panel called on the Ivorian government to carry out "exhaustive, impartial and transparent" investigations so as to ensure that justice would be done.

The authorities must already rapidly disarm those who are not part of the national defence or security forces, said the panel, which is led by Thailand's Vitit Muntabhorn, who served previously as the UN's investigator on North Korea.

The investigators' report is to be discussed at the Human Rights Council on 15 June, even as attacks continued in the west African state.

On Thursday, the UN mission in Ivory Coast accused Ouattara's forces of attacks and violence in the south and west that has left at least two people dead and dozens hurt.

The violence was in areas known to be home to supporters of ex-president Gbagbo, who is under house arrest after a nearly five-month dispute caused by his refusal to accept defeat in elections last November.

In May, Ouattara asked the International Criminal Court prosecutor to launch an inquiry into "the most serious crimes committed since 28 November 2010 throughout the Ivorian territory."