A video taken from a bus shows gridlocked traffic on Boar Lane on Saturday evening, with an ambulance unable to pass through.
There was traffic chaos across the city centre with delays of up to 40 minutes during peak times.
Metro Travel reported congestion on Great George Street, Merrion Sreet, Vicar Lane, Lady Lane, Eastgate and City Square to York Sreet via Boar Lane.
There was also standstill traffic on Kirkstall Bridge, Burley Road and Cardigan Lane.
First Bus reported delays of more than 30 minutes on services through the city centre, with residual delays expected into the evening.
The worst affected routes are service 35, 4, 16, 49, 50/50a and 56.