In the first operation, gardaí swooped on two Nigerians and seized 7kg of cocaine after stopping a taxi in Drumcondra, north Dublin, on Wednesday night.
Officers from the Garda National Drugs Unit found the drugs inside hidden compartments in suitcases.
The drugs are estimated to have a street value of about €440,000, but may be worth more if they are of high purity.
The two had been under surveillance by the drugs unit and customs officers after they arrived in Dublin Airport on Wednesday on a flight from Frankfurt.
Gardaí said international law enforcement agencies were also involved in what they describe as an ongoing operation.
Detectives arrested the two Nigerians, a man aged 67 and a woman aged 47. They were taken to Santry Garda Station and detained under Section 2 of the Drug Trafficking Act.
In a follow-up operation they arrested a 22-year-old Nigerian in Rathgar, south Dublin. She was taken to Ballymun Garda Station.
The arrests highlight the increasing involvement in west African gangs in the international trafficking of cocaine.
These gangs have established contacts with Irish gangs as well as eastern Europeans, who they sometimes use to courier drugs across the EU.
“We are trying to establish who they were going to supply the drugs to. It could be Irish nationals, or it could be other nationals,” said a garda source.
In the most recent operation against Nigerian traffickers, last November, drugs unit officer arrested a Nigerian man along with a South African and a British citizen.
In an unrelated operation, gardaí in Drimnagh, south-west Dublin, apprehended a man on a motorbike and seized a firearm.
Undercover garda units swung into action after receiving “reports of suspicious activity” at the rear of The Black Forge Inn on the Drimnagh Road.
A Garda spokesman said they followed a man on a motorbike.
“He was stopped and arrested and a firearm recovered nearby,” said the spokesman.
“A second man on a motorbike fled the area towards Bunting Road and a third man on foot was last seen going towards Slieve Bloom Park. These two men are still at large.”
He said the arrested man was taken to Crumlin Garda Station and detained under Section 30 of The Offences Against the State Act. He can be held for a maximum period of 72 hours.
The arrests follow the violent murder of Paul Keegan in nearby Walkinstown on Monday night. Gardaí suspect the 42-year-old rowed with people he had arranged to meet.