The roof of the minibus was sheared off in the crash

The accident, involving a minibus and three other vehicles, happened at about 0540 BST on Thursday, close to junction four.

Greater Manchester Police said those killed were four men and three women travelling in the minibus.

Fourteen passengers in five groups - from Herefordshire, Belfast, Leeds, Tyne and Wear and Fife - were on the minibus on their way to Manchester Airport.

A woman and a teenage girl were left critically ill in the crash, with six "walking wounded" also treated in hospital.

It is the utter carnage that is striking at the scene Derek Cartwright Ambulance service spokesman

The bus was taking the holidaymakers from the Britannia Country House Hotel, in Didsbury, Manchester.

They were due to fly to destinations including the US and Mexico.

It was pulling a trailer containing luggage - which was left scattered across the carriageway.

Police say the minibus collided with a Ford Mondeo, before hitting the central reservation.

The two other cars involved - a Vauxhall Vectra and a Toyota Carina - were hit by wreckage.

The accident happened close to a motorway patrol officer, who was parked in a police lay-by.

He administered first aid to the injured, with a nurse who also stopped to help.

The M56 was shut westbound between junction two and four.

Three lanes of the carriageway were later re-opened at 1335 BST.

Ambulance service spokesman Derek Cartwright described the initial scene as "utter carnage".

"It [was] a very, very difficult experience for people to take in."

Accident investigators were at the scene throughout Thursday morning.

'Extremely nasty'

Brendan Ryan, from Wythenshawe Hospital, said he spent several hours at the scene helping the emergency services deal with the aftermath of the crash.

He said: "It is difficult to put accidents on a scale, but certainly it was an extremely nasty event with a sizeable number of injuries."

Luggage was being pulled in a trailer behind the minibus

Greater Manchester Police said the minibus was fitted with seatbelts.

In a statement, the Britannia Country House Hotel said: "This is an awful tragedy and our deepest sympathy goes out to the friends and families of those involved."

Three of those with minor injuries, who are believed to be the drivers of the other vehicles, were later released after treatment.

The AA said the whole of south Manchester and parts of neighbouring Cheshire had been gridlocked with traffic after the accident.

A telephone helpline has been set up for friends and family on 0161 872 8178.