The Netherlands' former most wanted suspect and 16 other alleged members of a drugs gang dubbed the "Mocro-mafia" went on trial Monday in one of the country's biggest criminal cases.

Moroccan-born Ridouan Taghi, 43, and the others face charges including murder over an alleged campaign of assassinations by what prosecutors called a "well-oiled killing machine."

Taghi is the alleged mastermind of the Amsterdam-based group, seen as one of the Netherlands's largest cocaine distributors. He was arrested in Dubai in 2019.

Judges opened the hearing at a heavily secured courthouse nicknamed "The Bunker" on the outskirts of Amsterdam, Dutch news reports said.

Police are believed to have brought Taghi to court by helicopter, public broadcaster NOS said.

"In the case file a picture emerges of a well-oiled killing machine. A human life was worth nothing, given at least two murders involving mistaken identities," prosecutors said.

The 17 suspects are accused of murder and attempted murder, including ordering 13 hits of which six were actually carried out, prosecutors said in a statement.

The killings, carried out between 2015 and 2017, are believed to be connected with the gang's battle to control the Dutch cocaine trade.

The trial began at a heavily secured courthouse nicknamed "The Bunker" on the outskirts of Amsterdam
The trial began at a heavily secured courthouse nicknamed "The Bunker" on the outskirts of Amsterdam ANP / ROBIN VAN LONKHUIJSEN

The gang is nicknamed the "Mocro-mafia" because its members are mainly of Moroccan and Antillean origin.

Taghi denies all charges, saying money spent on a "sham trial could rather have gone to employing more teachers and police and health care," Het Parool newspaper reported.

Taghi was arrested in Dubai in December 2019, where he spent three years after entering on a passport in someone's else's name. Dutch police flew him back to the country by chartered jet.

Prosecutors say a breakthrough in the case came in 2017, when a man named as Nabil B. came forward as a witness following the mistaken-identity murder of a man in the Dutch city of Utrecht.

Nabil B., who was present in court on Monday, "was willing to make statements about a series of liquidations," they said.

"He spoke not only about his own involvement in those murders, but also about those who gave the orders and others involved," prosecutors said.

Prosecutors also based their case "on a large number of encrypted messages in which the suspects spoke about liquidations," ANP news agency said.

Security around the case is extra-tight as a lawyer for a state witness in the trial was shot dead near his home in Amsterdam.

The trial is expected to run until at least 2022.