The Nigerian army has analyzed video footage found in captured Boko Haram camps that indicates foreign fighters hold positions of power within the Nigerian militant group. The gruesome footage, reported Wednesday by Reuters, also showed amputations, stoning and lashing in the most convincing evidence yet to support the claim that Boko Haram has foreign influence within its ranks.

“The [foreigners] carry arms and fight alongside the other terrorists,” a senior military source, who declined to be identified, told Reuters in Abuja. “They are also experts and trainers.”

The half-hour video showed Boko Haram leaders in front of a large crowd ordering judgments based on the Islamist extremist group’s strict interpretation of Shariah law. A man whose face was covered by a white turban stood in the middle of the crowd and spoke in Sudanese Arabic. Another man wearing a black turban stood close by, speaking in Arabic and nodding in agreement, while another waved a Boko Haram flag behind them. Turbans in this style are not typical in northeast Nigeria, Reuters reported.

“God ordered all believers to enforce his punishments,” the man said to the camera while standing near a preacher who shouted into a loudspeaker in Nigeria’s northern Hausa language. “God ordered us to cut off the hand of the thief and flog the adulterer and adulteress.”

The crowd cheered as men and women were lashed, while others had their hands amputated. One man was stoned to death after being buried up to his head in a pit. There is no time stamp or date on the video, but the Nigerian military reportedly believed the gathering took place in southeastern Borno state in or near the town of Gwoza, Boko Haram’s former headquarters.

“It helps document their atrocities as evidence in the event of any trial,” a senior military source told Reuters. “To understand their pattern or mode of operation … and equipment in their possession with other information, is vital for intelligence.”

Nigerian troops found thousands of euros on the dead body of a Boko Haram commander in Borno state near the border with Cameroon this week. Nigeria Defense spokesman Maj. Gen. Chris Olukolade said the terrorist kingpin is believed to be of foreign descent and was among several Boko Haram fighters killed over the weekend during a foiled attack on Nigerian Special Forces in Mafa district, according to local media reports.

Boko Haram, which loosely translates in Hausa as “Western education is sinful,” pledged allegiance to the Islamic State group, also known as ISIS or ISIL. ISIS accepted the Nigerian militant group’s pledge in March. Boko Haram launched an insurgency in northeast Nigeria in 2009 to establish a state under strict Shariah law. Since then, more than 15,000 people have died in Nigeria, and nearly 1.5 million have been displaced, according to the United Nations refugee agency.