Lagos, Nigeria (CNN) -- An Iranian man, identified in court papers as a member the Iranian Revolutionary Guard, was charged Thursday with importing 13 containers of mortars and rockets into Nigeria last month.
Three Nigerians, including two who worked as customs clearing agents, also were charged in the alleged arms shipment conspiracy, court documents said.
Iran called the arms shipment a misunderstanding.
"A private company which had sold conventional and defensive weapons to a West African country had transferred the shipment through Nigeria," Iran's state-run Press TV quoted Iranian Foreign Minister Manouchehr Mottaki as saying.
Nigerian Foreign Minister Odein Ajumogobia, who said he had "a useful meeting" with Mottaki, called the shipment "troubling." He said Mottaki pledged cooperation with the investigation.
Ajumogobia said the original bill of lading showed the shipment was destined for Nigeria but another bill of lading surfaced later indicating it was destined for Gambia.
The court identified the Iranian as Azim Aghajani, a businessman from Tehran who was also member of the Iranian Revolutionary Guards.
"He's being interrogated as we speak by the security agents to find out more," Ajumogobia told CNN in an recent interview. "He's been cooperating with the security agents."
The Nigerians charged in the conspiracy, which allegedly began in July and ended with the seizure in October, were clearing agents Aliyu Oroji Wamako, 47 and Muhammen Tukur Umar, 40, and Abuja businessman Ali Usman Abbas Jega, 45.
The seizure has been reported to the United Nations Security Council, he said.
CNN's Christian Purefoy contributed to this report.