The Nigerian army has cited a video of US President Donald Trump, in which he says soldiers should respond with force to migrants throwing stones, to justify opening fire on a Shia group this week.
"When they throw rocks... consider it as a rifle," Mr Trump says in the clip.
Nigerian police have arrested 400 members of a Shia Muslim sect after days of deadly protests in the capital.
Amnesty International has criticised Nigeria's army for the killings, saying the Shia protesters were peaceful.
But a spokesman for the Nigerian army says their decision to fire live rounds at protesters in Abuja was justified because they were armed, telling the BBC "this is what [Mr] Trump was talking about".
The army's official Twitter account shared the video adding the caption "please watch and make your deductions".
The clip shows the US president saying, in reference to Central American migrants, "they want to throw rocks at our military, [then] our military fights back".
Please Watch and Make your Deductions. pic.twitter.com/05yVwULFoh— Nigerian Army (@HQNigerianArmy) November 2, 2018
Nigeria Army spokesman Brig Gen John Agim says the army posted the video in reaction to the rights group's report accusing the army of using weapons against Shia protesters.
The army did not mention the fact that the US embassy in Abuja has urged Nigerian authorities to "take appropriate action to hold accountable those responsible for violations of Nigerian law".
We urge Government of Nigeria authorities to conduct a thorough investigation of the events and to take appropriate action to hold accountable those responsible for violations of Nigerian law.— U.S. Mission Nigeria (@USEmbassyAbuja) November 1, 2018
The number of Shia Muslim protesters killed by Nigeria's army in the capital, Abuja, in clashes which began at the weekend, has not been independently verified.
The Nigerian army says six protesters have been killed, but the protest group itself says dozens died, and rights group Amnesty International says the true number is 45.
Members of the Islamic Movement of Nigeria (IMN), have been demanding the release of their leader Ibraheem Zakzaky who has been in custody for 34 months.
Disputing Amnesty's statement that protesters were unarmed, Brig Agim told the BBC "police found 31 petrol bombs with the protesters as well as guns, knives and stones".
"The Shia people always obstruct the work we're doing," he added, saying they had blocked an arms convoy at the weekend and overrun a checkpoint on Monday.
Brig Agim said it was "not true that they were protesters", and described them as "the aggressors".
Shias in Nigeria
- Shias are minority in Nigeria but their numbers are increasing
- The IMN, formed in the 1980s, is the main Shia group led by Sheikh Ibraheem Zakzaky
- They operate their own schools and hospitals in some northern states
- They have a history of clashes with the security forces
- The IMN is backed by Shia-dominated Iran and its members often go there to study
- Sunni jihadist group Boko Haram condemns Shias as heretics who should be killed.