A Lithuanian gang allegedly supplying heroin on the streets of Belfast recruited replacement dealers as members were arrested, the High Court heard on Friday.
Even though police detained more than 20 suspects in a major undercover operation, a judge was told new sellers have been brought in to continue the drugs trade.
Details emerged as bail was refused to one alleged member accused of dealing to officers on four separate occasions.
Donatas Kiaulakis, 30, faces a total of 16 charges including multiple counts of possessing and supplying heroin and acquiring criminal property.
Refusing bail, Mr Justice Gillen said: “That organised professional gangs should be involved in the supply of drugs in Northern Ireland is a frightening development.”
Police targeted those suspected of involvement in distributing heroin during an operation earlier this year.
Kiaulakis, with an address at Chobham Street in Belfast, is alleged to have sold to undercover officers on dates in January and February.
CCTV footage forms part of the case against him.
Prosecuting counsel said he was one of 21 people detained - nearly all of them being Lithuanian nationals.
“Following this operation further arrests have been made; the gang replaced the persons selling drugs with new recruits,” the barrister told the court.
According to Kiaulakis’ legal team he moved to Belfast from the Republic last year and worked as a fisherman.
Seeking bail, his lawyer argued that he is only alleged to have sold small amounts of heroin.
“He’s unlikely to see a trial date this year,” he added.
But Mr Justice Gillen refused the application due to risks that the accused may flee or commit further offences.
“Drugs are a real menace in Northern Ireland, they are a source of much crime and profound misery,” he added.
“This gang of which it’s alleged he is a part, according to police, continue to supply Class A drugs.
“If the police case is correct he participated four times and has been of no assistance to police since his arrest.”