Police in Scotland have warned that the death toll will rise after confirming that one person was killed when a helicopter crashed into a pub in Glasgow on Friday night.

Witnesses report the helicopter falling from the sky "like a stone" at about 10:35pm on Friday, and crashing on to the roof of the Clutha pub in Stockwell Street.

Chief Constable Sir Stephen House confirmed that one person had been killed and 32 injured.

He said there was "deep sorrow" in Police Scotland and thoughts were with all those involved.

Sir Stephen said that specialist teams were working to stabilise the building in a "difficult and sensitive" operation and said: "Our prayers are that we do recover people alive."

He said: "There are people on the scene trying to make contact with anyone who may be alive at the scene. All we can do is confirm there has been one fatality but we are certain there will be more."

He could not say when contact had last been made with someone trapped inside.

Sky News reported that at least six people have died, while - in a reflection of the confusion surrounding the incident - the BBC put the number of fatalities at three.

Scotland's first minister Alex Salmond said: "This is a black day for Glasgow and Scotland but it is also St Andrew's Day and we can take pride in how we respond to adversity.

"The response from our emergency services and citizens has been exemplary."

In the aftermath, passers-by rushed to help the injured, forming a human chain to pull them from the wreckage and off-duty medics identified themselves and helped to treat those rescued.

Among those who ran to help was Labour MP Jim Murphy, who was driving by the pub at the time of the crash.

He told the BBC there was "pandemonium" as people tried to get out.

"It was almost like slow motion," he said, adding: "People just formed a bit of human chain, side by side with each other, to help pull injured people out."

The shadow cabinet minister, who had blood on his shirt which he said was not his, described what he saw as a "horrific scene".

It is believed that there were about 120 people in the pub at the time, watching a gig by a local band. Many were trapped when the left side of the building collapsed.

Two police officers and a civilian pilot were on board the helicopter at the time of the crash, police said.

Witnesses say that many did not know what had happened in the immediate aftermath of the crash.

Eyewitness Fraser Gibson, 34, was inside the pub with his brother to see his former band, Esperanza.

"Part of the room was covered in dust. We didn't know what had happened. We froze for a second; there was panic and then people trying to get out the door," he told the BBC.

Wesley Shearer, who was inside the bar at the time, tweeted: "The roof in the Clutha Bar just collapsed mid gig. People have been caught under it and smoke everywhere." He added later: "This is unbelievable. Just spent 20 minutes pulling people out of the bar."