Detectives investigating the murders of an underworld "Mr Big" and a mob "fixer" have arrested three more people.
Police arrested a 49-year-old man in Rochdale and a 30-year-old woman in Salford on suspicion of conspiracy to commit murder and another woman, aged 35, was also arrested in Salford on suspicion of perverting the course of justice in relation to the murder of Paul Massey.
They come after three arrests on Wednesday for the murders of Massey and John Kinsella following a joint operation by Merseyside and Greater Manchester Police (GMP).
Massey, 55, gunned down outside his home in July 2015, was a well-known figure in his home city of Salford and had been involved in security firms operating in Manchester and beyond.
Kinsella, 53, shot dead earlier this month in St Helens, Merseyside, had been a mob fixer who once stopped a gangster terrorising former Liverpool FC footballer Steven Gerrard.
Dawn raids were executed at addresses in the Heywood, Rochdale and Salford areas of Greater Manchester as well as in Cheshire on Wednesday.
One man, aged 37, was arrested at Manchester Airport on suspicion of the murder of Paul Massey and the murder of John Kinsella.
A 39-year old woman was also arrested at the airport on suspicion of assisting an offender in relation to the John Kinsella murder.
A 48-year-old man was arrested in Salford on suspicion of conspiracy to murder in relation to the Paul Massey murder investigation.
All six remain in custody for questioning, police said.
Detective Chief Inspector Carl Jones, of GMP's Major Incident Team, said: "Following on from yesterday's arrests we have three more people in custody who will be questioned by detectives in relation to Paul Massey's murder.
"This means we now have six people in custody and our enquiries are continuing at this time."
Massey, a father-of-five, died in a hail of bullets as he stepped out of a silver BMW car outside his home in the Clifton area of Salford almost two years ago.
He was blasted four times by an assassin wearing "military style" clothing for the apparent gangland hit.
His fearsome reputation grew during the drug-fuelled 90s rave scene in Manchester.
John Kinsella died after being shot while walking his dog with his partner on a footpath, near to the St Helens Linkway and the M62 motorway at 7am on Saturday, May 5.
Kinsella had served time in jail for his part in a £41,000 robbery in Grantham, Lincolnshire in 2006.
He went on the run shortly before a jury found him guilty of stealing thousands of pounds worth of detergents, crisps and Easter eggs.
During his trial, the jury heard how Kinsella had stopped a gangster terrorising then Liverpool football star Steven Gerrard.
The court was told Kinsella was asked by Paul Gerrard, the footballer's father, to intervene after he said his son was being terrorised by a gangster known as the "Psycho".
In a letter that was read out in court Mr Gerrard Senior told of his family's gratitude after "threats from the Liverpool underworld" stopped.