The United States has called on Nigerian officials to investigate the clashes between army troops and a Shi'ite Muslim sect that reportedly left hundreds of people dead.
The U.S. embassy in Abuja said Wednesday that the Nigerian government should "quickly, credibly and transparently investigate these events... and hold to account any individuals found to have committed crimes."
A video posted to YouTube purportedly shows the initial confrontation Saturday between the army and members of the Islamic Movement for Nigeria (IMN) in the northern town of Zaria.
Officers are seen arguing with civilians blocking a highway, demanding that the convoy of army chief General Tukur Buratai be allowed to pass.
WATCH: Video purportedly shows initial clash
After several minutes of negotiations, young men chanting slogans and armed with sticks and stones approach the convoy. The tape then cuts to a scene when the army troops and vehicles are advancing down the road, past burning tires in the street.
Activists and sect leaders say up to 1,000 Shi'ite Muslims were killed in army raids that followed the initial confrontation.
The army said troops were responding to what it calls an assassination attempt on Buratai. The IMN said the army was carrying out a pre-planned attack.
The army has said it has IMN leader Ibraheem Zakzaky and his wife in custody.
The IMN seeks to establish an Islamic state in northern Nigeria and is known to have links to Iran. On Tuesday, Iran's foreign minister summoned the top Nigerian diplomat to Tehran to protest the killings, while the Iranian parliament demanded an investigation.
The IMN is not connected to Boko Haram, the Islamist radical sect blamed for more than 10,000 deaths in Nigeria over the past six years.