A 32-year-old man was arrested in Co Armagh yesterday on suspicion of conspiracy to commit murder.
The PSNI said he was detained following searches in Crossmaglen as part of the National Crime Agency-led operation, Operation Venetic.
Mobile phones, cash and four vehicles were seized during the raids.
A PSNI spokesman said: "The male was arrested on suspicion of a number of offences, including conspiracy to commit murder and drugs offences involving Class A, Class B and Class C drugs".
He remained in custody last night.
Operation Venetic targets organised crime groups using encrypted technology in a bid to evade law enforcement
Led by the National Crime Agency, it has been described as the UK’s biggest law enforcement operation against serious and organised crime.
Raids were also carried out in Northern Ireland last week.