At least eight people were killed and dozens injured when a police helicopter crashed into the roof of a packed Glasgow pub, trapping many inside in choking dust and debris, Scottish police have said.

Five people were killed inside the pub and three in the helicopter, police told the Associated Press news agency.

Witnesses said the helicopter dropped from the sky like a stone onto the busy Clutha Pub in Scotland's biggest city at 10:25 pm on Friday night as over 100 people listened to a live music concert.

Emergency workers on Saturday morning were still searching through the rubble for survivors in the shadow of the mangled blue helicopter, which was embedded in the pub's roof.

"Sadly at this time I can confirm one fatality. We expect that number to increase over the coming hours," Chief Constable of Police Scotland Stephen House told reporters, adding 32 people had been taken to hospital.

'Black day for Glasgow'

There were three people aboard the helicopter, two police officers and a civilian pilot, when it crashed.

House said the recovery operation would take some time and he could not confirm if anyone was still thought to be alive.

Paul Watt, a regular at the Clutha pub, had not gone to the pub on Friday because he was working that evening [Reuters]

The 12-metre helicopter carrying two police officers and a civilian pilot spiralled into the pub in a busy area of Glasgow, destroying part of the roof.

Police said it was too early to speculate on what caused the Eurocopter EC135 T2, made by a subsidiary of EADS, to come down.

The aircraft did not appear to have caught fire. The Air Accident Investigation Branch has begun an investigation.

"This is a black day for Glasgow and for Scotland," Scottish First Minister Alex Salmond said, noting that Saturday was St Andrew's Day, Scotland's national day.

He praised the "instinctive courage of ordinary Glaswegians going to assist their fellow citizens in extremity".

Source: Al Jazeera and agencies