The Islamic State group, which is said to be the world’s wealthiest terrorist organization with diversified sources of funding, received up to $45 million in ransom in the past year, according to a United Nations expert.

Yotsna Lalji, who monitors sanctions against al Qaeda, said in a meeting of the U.N. Security Council's Counter-Terrorism Committee that as much as $120 million in ransom was estimated to have been paid to terrorist groups between 2004 and 2012, and ISIS collected between $35 million and $45 million in 2013 alone, The Associated Press (AP) reported.

According to Lalji, al Qaeda and its affiliates have made kidnapping “the core al-Qaida tactic for generating revenue,” in recent years. She also pointed to a 2012 video recording in which al Qaeda leader Ayman al-Zawahri provoked militants worldwide to abduct Westerners.

Lalji said that al Qaeda in the Arabian Peninsula, operating from Yemen, received $20 million in ransom between 2011 and 2013. On the other hand, al Qaeda in the Islamic Maghreb, operating in North Africa, got $75 million over the past four years, AP reported.

Last week, the U.N. released a report stating that ISIS has multiple sources of funding and possesses enough weapons to carry on fighting for two more years. The U.N. also proposed imposing sanctions on ISIS to help cut off the flow of funds to the group. According to the U.N., ISIS is capable of producing nearly 47,000 barrels of oil each day, and it charges $18 to $35 a barrel, and based on the estimated daily production, the group’s projected potential revenue from crude oil could range between $846,000 and $1,645,000 a day.

There have been reports that ISIS is also trafficking in women and children in local markets. On Monday, the group released a video, entitled “The Blood of Jihad 2,” which shows how young children undertake tough military training in ISIS camps before they are sent off to fight for the group's cause of building an Islamic caliphate in the region.

The latest video is the second in a series revealing life inside the rigorous training camps of ISIS. The first part was released in October, depicting the training and graduation of adult recruits for the militant group.