A Libyan human rights organisation has accused the Libyan National Army (LNA), led by General Khalifa Haftar and its militia supporters in Benghazi, responsible for acts that amount to "crimes against humanity".

In a report calling on the international community to intervene, Human Rights Solidarity said a "mass killing" that claimed six lives last week was the third of its kind since Haftar took control of the city last month.

The LNA and other armed groups loyal to Haftar are operating under the mantra of "Operation Dignity", which they claim is a fight against "terrorism".

Libya has been engulfed in a civil war since a 2011 popular uprising ended Muammar Gaddafi's 42-year rule. Rival governments, including the UN-backed Government of National Accord (GNA), have been fighting for control over the country.

Al Jazeera spoke with Ahmed el-Gasir, a senior Libya researcher with Human Rights Solidarity, who said that Libya's culture of impunity will take years to abolish.

OPINION: How we are failing Libya

Al Jazeera: The report asserts that there is a "culture of impunity" in Libya. Why is that?

Ahmed el-Gasir: The culture of impunity prevalent in Libya is a result of the inability of judicial and law enforcement authorities to function in the country. Perpetrators of grave violations, such as extrajudicial killings and torture, document their crimes, videos and photos, and broadcast them without fearing accountability.

Since Gaddafi's regime ended, apart from the trials of ex-regime members and associates, there were no trials carried out for any of the serious crimes committed by any party.

The inability and failure of these authorities to operate is mainly caused by the spread of weapons, the presence of hundreds of militias and political chaos in Libya, with several entities claiming "legitimacy".

Al Jazeera: Why have the Libyan authorities and the various sides involved been unable to protect civilians?

Gasir: The central authority, which is the government, is weak. It does not have the power to enforce rule of law. The internationally recognised government and the unrecognised governments, all have no forces that operate under their control, which has been the case with all transitional authorities since 2011.

They rely on armed militias, who have their own allegiances and agendas, to carry out security and military tasks. On paper, the militias operate as part of the Ministry of Interior, but in reality, they follow their own chain of command.

We have to remember that even before the revolution, law enforcement agencies and various police departments were neglected by the previous regime. The security apparatus of the regime was more organised, better trained and had more resources to protect the regime. When the regime collapsed, so did the security apparatus, leaving behind a security vacuum where it was too dangerous for law enforcement units to operate.

Al Jazeera: What can the international community do to ensure the safety of civilians in Benghazi and Libya as a whole?

Gasir: To close the "impunity gap", the international community - including the United Nations Security Council (UNSC), the European Union and the International Criminal Court (ICC) - needs to act.

UNSC Resolution 1970 from 2011 referred the case of Libya to the ICC, which has yet to officially announce opening investigations into violations of international law on the basis of a lack of resources. An official ICC investigation and the issuance of arrest warrants will send a clear message to perpetrators that they are going to be held accountable for their crimes and actions, with no impunity.

The tactics employed by Gaddafi in 2011 created certain divisions between towns or tribes, but they do not compare to what Haftar has done.

The EU can and should help, and it is in its interest that stability in Libya is attained. The most pressing issue for the EU is illegal migration. About 90 percent of arrivals by sea in Italy depart from Libyan shores. As the Libyan crisis continues, these criminal networks will grow more sophisticated and organised.

The EU and other international actors can also help by supporting the GNA in training and developing Libyan law enforcement agencies, and by identifying and targeting individuals and entities complicit in serious violations of human rights through the implementation of sanctions.

Al Jazeera: Why do you think the internationally recognised government is struggling to enforce the rule of law?

Gasir: Partially, because the GNA does not have its own forces, it relies on militias to operate in Tripoli. It is building a new force - the Presidential Guard - but this takes time. Promoting ideals of human rights is not on the GNA's priority list, unless it appeases the international community. The Libyan authorities have not initiated a single investigation into serious offences committed after the fall of the regime.

The GNA believes it is in need of militias affiliated to the interior ministry to operate - a dangerous misconception. In fact, it is these armed groups that are in need of the GNA and its resources. Legally, the GNA is responsible for the crimes these militias commit.

Al Jazeera: What do you think Khalifa Haftar aimed to achieve when he launched "Operation Dignity"?

Gasir: Haftar claimed that it was aimed at "fighting terrorism", but many perceived it as it is - a military coup.

The proclaimed "war on terrorism" is just an excuse as he attempted to gain control of Tripoli earlier in 2014, but failed when his militias in support did not show up. In that attempted coup, he announced the suspension of congress and the government, without referring to "terrorism".

Al Jazeera: Do you think the tactics employed by Haftar's fighters and other armed groups will create a deeper divide between the Libyan people?

Gasir: "Operation Dignity" has adversely affected the social fabric of Libyan society. The tactics employed by Gaddafi in 2011 created certain divisions between towns or tribes, but they do not compare to what Haftar has done.

Hate speech and incitement of violence divided not only towns or tribes, but also neighbourhoods and even families. The level of violence and disregard to the sanctity of human life and value of human dignity is unprecedented in Libyan society.

It will be a lengthy process to overcome what criminality the group managed to achieve thus far.

This interview has been edited and condensed.