A total of £170,000 in cash and a stun gun were seized during searches at various locations in Armagh yesterday, Wednesday, July 133.
Three men aged 31, 38 and 58, and a 56-year-old woman were detained.
Police say the operation started when officers “forcibly stopped” a van on the Killylea Road around 3 pm.
A 38-year-old man, who was driving the van, was arrested at the scene after officers found £10,000 inside the vehicle.
During a follow-up search of a house on Salters Grange Road, Armagh, police seized a Mercedes S63 AMG, a BMW X5 and documents.
Half an hour later, a 31-year-old man was arrested at a filling station on Cathedral Road in the city.
Officers then went to an address in Callan Crescent, where they found about £160,000 hidden in the living room.
The search also netted a stun gun and four “extremely high-end designer watches” at the property.
The 56-year-old woman and the 58-year-old man who were in the property at the time were arrested for questioning.
A police spokesman said officers believed the cash and jewellery were the “proceeds of major drugs criminality”.
“We believe this operation has struck a major blow to the activities of an organised gang involved in serious drugs criminality in Northern Ireland,” he said.
All four are still in custody being questioned under the Misuse of Drugs Act 1971 on suspicion of drug, possessing criminal property and money laundering offences.