London Fire Brigade (LFB) was at the scene in Moorgate on Thursday lunchtime.
The brigade said shortly before midday that around 40 firefighters in six engines were responding to the blaze, near the Barbican.
The LFB added that around 1,200 people were evacuated from the neighbouring buildings as a precaution. The cause of the fire remains unknown.
“A large amount of smoke is being produced,” it warned.
City of London Police said several roads in the area – Moorfields, Wood Street and Fore Street – are closed to traffic due to the fire.
Dillan Patel, 27, who works in tech at the Ropemaker Building, was due to arrive at the office around lunchtime. He received a message from his colleagues at midday telling him the building had been evacuated.
He told the Standard: “I believe the fire was at one of the adjacent buildings.”
One eyewitness said: “It was above the Rack and Tenter pub, by Citypoint. There were flames and smoke coming out of the top.”
This is a breaking news story. More to follow.
https://www.standard.co.uk/news/london/fire-moorgate-barbican-city-london-black-smoke-building-police-roads-closed-b1101288.html Buildings evacuated and roads closed after fire in Moorgate