Nigerian officials say they have seized heroin worth nearly $10m (£6.25m), concealed in engine parts shipped from Iran.
The National Drug Law Enforcement Agency (NDLEA) said agents made the seizure at Apapa seaport in Lagos.
The haul comes just days after Nigeria reported Tehran to the UN Security Council over an illegal arms shipment from Iran that was intercepted.
West African ports are key transit hubs for drugs heading to Western markets.
NDLEA spokesman Mitchell Ofoyeju said the agency had received "strong intelligence" from "foreign collaborators" four months ago, so it had been monitoring the consignment before it arrived in Nigeria.
"The NDLEA... decided to get a welder to cut open the engine parts and behold, we found hidden inside them 130kg (20 stone) of heroin," said Mr Ofoyeju.
A customs spokesman told AFP the drugs were brought into Nigeria aboard a foreign vessel, the MV Montenegro.
Three Nigerians have been arrested in connection with the drugs shipment.
In October, Nigerian security forces found a shipment of weapons at the same port.
Rocket launchers, grenades, explosives and other weapons were found in containers labelled as building materials shipped from Iran.
Iran said the weapons were the subject of a "misunderstanding", which had been cleared up.