(CNN) Libyan officials have denounced the migrant slave auctions exposed in a CNN investigation , but claim more support is required from the global community to tackle the issue.

The United Nations-backed Libyan Government of National Accord, or GNA, said it's keen to address violations against illegal immigrants but called upon regional and global partners to provide assistance.

Libya "is going through difficult times which affected its own citizens as well. It is, therefore, not fair to assume responsibility for the consequences of this immigration, which everyone unanimously agreed that addressing this phenomenon exceeds the national capacities," the GNA statement read.

"We affirm again that the practical solution is to address the real reasons that drive people to leave their home countries, treat them and develop final solutions for them," it continued.

On Tuesday, Libya's Ministry of Foreign Affairs reiterated that a committee has been established to investigate the auctions but asked "the international community to intensify in a spirit of responsibility and joint cooperation to assist Libya."

Smugglers exploit migration crisis

A CNN team traveled to Tripoli last month after obtaining footage of a migrant auction. While there, they witnessed a dozen men being auctioned off for as little as $400 each.

CNN was told of slave markets at nine locations across Libya, but many more auctions are believed to take place each month. CNN believes some of the auction sites are in territory controlled by the GNA, but others are not; the GNA does not control the entire country.

In recent years, Libya has been flooded by migrants hoping to travel to Europe. The United Nations estimates there are now between 700,000 and a million migrants in the country. Those who have crossed the Mediterranean have shared stories about beatings, kidnappings and enslavement.

The UN Secretary-General António Guterres said Monday he was "horrified" at reports of migrants being sold as slaves, which could amount to crimes against humanity.

Guterres called on the international community to unite on the issue and said the auctions were a reminder of the need to manage migration flows in a humane manner that addresses the root causes, increases opportunities for legal migration and cracks down on smugglers.

In recent days, there has been a growing chorus of condemnation and calls for urgent action from state officials including France and Spain.

Spain's foreign ministry on Wednesday expressed its "deep concern" over the CNN report which shows "an appalling treatment of African immigrants during an alleged auction in Libya." Spain urged Libya to follow the UN against transnational crime and human trafficking, the Foreign Ministry said on its official Twitter account.

Seeking help from African Union

Despite the chaotic situation in Libya, the GNA claims it's been working to combat exploitative smugglers operating in the country.

Mohammed Bisher, head of the government's Anti-Illegal Immigration Authority, said detention facilities are overwhelmed and he urged countries from which migrants travel to take more responsibility.

"We are 278 million Libyan dinars (nearly $210 million) in debt. We have to provide food, medicine, transportation... If the African Union wants to help, they can help," Bisher told CNN.

Bisher said Italy has been providing some assistance, coordinating with Libyan officials and, in some cases, helping with deportation but more needs to be done.

"Deportation is a logistical problem between the International Organization for Migration (IOM) and the embassy representatives. We are ready to deport at any time," Bisher continued.

"The countries these migrants came from did not take them back or contribute help for them inside Libya... We have only deported 5% of the 20,000 in the detention centers because of the lack of response from the governments of where these people are from."

Alpha Conde, president of the African Union and Federica Mogherini, European Union foreign policy chief, vowed to assist Libya in swiftly combating the issue of human traffickers in Libya after speaking on the phone on Monday, according to a joint press release.

Detention centers are full

In September, officials conducted raids in the Libyan coastal city of Sabratha, saying they rescued thousands of migrants from warehouses and farms, where some had been sold into forced labor.

Before the raids, the government's Anti-Illegal Immigration Authority said approximately 8,000 migrants were being held in detention centers awaiting deportation.

The immigration authority told CNN on Tuesday an estimated 25,500 migrants, 4,000 of them from Nigeria, were now being held at various detention centers in the country.

However, Abike Dabiri, senior special adviser to Nigeria's president of foreign relations and diaspora, said repatriation is not straightforward.

"The first thing is to determine who the Nigerians are. Everybody says they are Nigerians but what we have to do is to profile those who are coming back," explains Dabiri.

Over 5,000 Nigerians have returned from Libya in the last six months, she claims, but progress is slow "because of lack of governance in Libya."

"We have been asking Libya to return them to Nigeria so they have been returning them in batches."

Dabiri said she hopes to get approval from the Nigerian government to send a delegation to Libya in early December to visit the detention centers and expedite Nigerian citizens' return home.

Libyan officials concede that the detention centers like Treeq Alsika in Tripoli are crowded, but insist they are doing what they can to help migrants return home.

EU migration chief: Responsibility falls on world's shoulders

On Friday, Dimitris Avramopoulos, the European Commissioner for Migration, described the footage of slave auctions as "shocking."

He said the EU was working with international partners in the country and added that the migration crisis was "not only the responsibility of the European Union but the responsibility of the whole world."

"On smuggling and trafficking, we see the very ugly reality in your video and tackling this is a core priority for us," he added.

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The International Organization for Migration, an intergovernmental organization based in Geneva that focuses on managing migration, has welcomed Libya's investigation into the trafficking of migrants. But Othman Belbeisi, its chief of mission for Libya, warned that "the smuggling networks are becoming stronger, more organized and better equipped."

Human Rights Watch senior Libya researcher Hanan Salah said she hopes the Libyan authorities will handle the situation in a timely manner.

"Libyan interim authorities have been dragging their feet on virtually all investigations they supposedly started, yet never concluded, since the 2011 uprising," Salah told CNN. "We urge Libyan authorities to take this matter seriously, and make good on their pledge to investigate such allegations by conducting a speedy and transparent inquiry into alleged 'slave auctions.'"

"We also urge the Government of National Accord to hold perpetrators to account and make public their findings."