The Scottish Police Federation (SPF) has said an officer has been stabbed during a major incident in Glasgow.
The organisation, which represents rank and file police officers, said the family of the officer has been informed.
Police Scotland said there is no danger to the public, with officers in attendance in West George Street in the city centre on Friday afternoon.
Images on social media appear to show armed police entering a building and a large number of emergency vehicles outside.
The SPF tweeted: “We are aware of reports a police officer has been stabbed in an incident in #Glasgow city centre.
“Our officials are in attendance to provide all necessary support. Please allow our collages the space to do their jobs. Further updates will be provided when we are able to do so.
It added: “We appreciate families of police officers in #Glasgow will be anxious to hear that a police officer has been stabbed. Please be aware the family of the officer has been notified and is being supported by the service.
In a statement on Twitter, police said the incident is “contained” and there is no danger to the general public.
Greater Glasgow Police tweeted: “Emergency services are currently dealing with an incident on West George Street in Glasgow.
“The street is currently closed off and the public are asked to avoid the area at present.
“The situation is contained at this time and there is no danger to the general public.”
Scotland First Minister Nicola Sturgeon tweeted: “Please follow advice to avoid the West George Street area of Glasgow while @policescotland deal with this ongoing incident.”
Witness Craig Milroy, who saw the aftermath of the incident from an office building nearby, said he had seen four people taken away in ambulances.
He told the PA news agency: “I saw a man lying on the ground, of African descent, with no shoes on. He was on the ground with someone holding his side – I don’t know if it was a bullet wound, a stab wound, or what it was.”
Mr Milroy said the man was one of the four taken away by medics and believed him to be a victim of an attack.
He added: “After that we saw commotion, ambulances further up and we saw armed police all running into the hotel next to the Society Room.
“We were still standing outside, after that the police all came down, the riot police and triage team told us to go back in and lock the door.”
A traffic information bulletin issued by Glasgow City Council said a number of roads in the city centre had been closed.