Ivory Coast's army has committed "widespread human rights violations" against supporters of ousted former president Laurent Gbagbo, Amnesty International said in a report published Tuesday.

A restructuring of the Ivory Coast Republican Forces (FRCI), to incorporate former rebels, began after a violent post-electoral crisis which lasted from December 2010 to April 2011, claiming about 3,000 lives while Gbagbo refused to concede defeat at the polls to President Alassane Ouattara.

The international human rights watchdog found during a visit to Ivory Coast in September and October last year that "this new national army, along with an armed militia of traditional hunters, the Dozos, are carrying out extra-judicial executions, deliberate and arbitrary killings, politically motivated arrests and torture".

"They are acting with almost total impunity under the pretence of ensuring security and fighting against perpetrators of armed attacks," the report said.

The Amnesty team heard first-hand evidence about how detainees, largely seized for their political or ethnic affiliations, were being held for months, with no access to their families, doctors or lawyers.

Some families did not know where their relatives were until being contacted by Amnesty delegates, who visited several places of detention, "including two unofficial ones", and heard accounts of torture with electricity or molten plastic to extract confessions about alleged participation in armed attacks.

"The Amnesty International delegation was able to meet all of Laurent Gbagbos relatives and aides held in five detention centres in the centre and north of the (west African) country," the report said. "Some of them have been subjected to inhumane and degrading treatment."

Gbagbo himself has been detained by the International Criminal Court in The Hague since the end of 2011, on suspicion of crimes against humanity. Many of his supporters are still detained in Ivory Coast.

The United Nations, Amnesty International and other non-governmental organisations previously accused the FRCI of serious rights abuses when the army responded to a wave of sometimes deadly attacks in the latter half of 2012.

These attacks targeted the security forces and strategic sites. The government blamed the attacks on followers of the toppled regime, who denied the allegation.

Supporters of President Ouattara are also suspected of carrying out serious crimes during the political crisis of 2010-2011, but none of them have been brought to justice, any more than the soldiers accused of atrocities in response to last year's attacks.

Ivory Coast "needs to break the cycle of abuse and impunity," said Gaetan Mootoo, a West Africa researcher with Amnesty International. He denounced "an absolute failure to establish the rule of law and severely undermining the reconciliation process set up in July 2011".

The organisation also called for an international commission of inquiry into a July 2012 raid on a displaced persons' camp in Nahiby, near the western town of Duekoue, which targeted people mainly from the Guere ethnic group, considered to be pro-Gbagbo.

Fourteen people were reported killed, but Amnesty said "many more bodies are believed to have been dumped in wells".

This assault on a camp guarded by UN forces was carried out by youths from a Dioula quarter of Duekoue, an ethnic group considered close to the current regime. Rights organisations said government troops and Dozos were also involved.

An investigation opened by the Ivorian judiciary has so far led to nothing.

Mootoo warned that "If measures are not put in place immediately to control the security forces, (Ivory Coast) risks successive political crises, where national reconciliation becomes a long lost hope."

In a letter published as an annex to the report, the Ivorian justice ministry said that the authorities had made a commitment to track down alleged rights violators and added that "efforts deployed by the state" included training of the armed forces in respect for human rights.