The group gathered on North Parkway from 6pm and a 'core' of around 20 people are thought to be responsible for most of the anti-social behaviour in the nearby housing estates.
A 21-year-old rider was struck by a car and injured in nearby Osmondthorpe, but it is not known if he was part of the rideout. He collided with a car and a parked flatbed truck on Rookwood Avenue just after 8.30pm, and was taken to hospital with serious but not life-threatening injuries.
Fireworks were thrown during the terrifying Halloween violence and bikes were ridden on the wrong side of the road.
One woman said on Facebook that she had seen a rider overtaking a bus while pulling a wheelie.
West Yorkshire Police said:-
"Police are investigating an incident where motorbikes congregated in the Seacroft area of Leeds last night and were ridden dangerously and anti-socially.
"From about 6pm, officers on patrol in the area became aware of a gathering of up to 50 motorbikes and quads in the vicinity of North Parkway.
"A core group of about 20 were mainly responsible for the issues caused in North Parkway and South Parkway and around local estates.
"Groups of local youths and other bystanders added to the situation by encouraging the group and taking part in anti-social behaviour, including the misuse of fireworks.
"Officers were deployed to the area to deal with the situation and maintain public safety and also to gather evidence to assist in identifying those involved for further follow-up action.
"At one point, roads policing units had to close North Parkway to prevent bikes from riding the wrong way up the carriageway.
"By about 9pm there were no further reports of any issues in the area involving the motorbikes.
"Various offences have been identified and enquiries are ongoing to trace those involved and take appropriate action."
Chief Inspector Sally Fryer, who leads Neighbourhood Policing, said:
“The behaviour by this group last night was completely unacceptable and put people’s safety at risk and caused unnecessary fear to members of the public, including children and families out for Halloween.
“We will not allow this kind of illegal activity that impacts on people’s lives to go unchallenged. Our focus during the incident last night was primarily on ensuring public safety while attempting to disrupt and deter the activities of this group and gather evidence on those involved.
“We will now be reviewing all the available evidence, including CCTV and officers’ body-worn video footage from last night, to identify those involved and arrest them and seize their vehicles.
“Our investigation into the significantly larger ‘rideout’ event in 2016 led to 13 people being given prison sentences for causing a public nuisance.
“That should serve as a very clear reminder to anyone who unwisely involves themselves in similar activity of the type of penalties they can face.
“We would also remind people that a special injunction remains in place, which bans anyone from taking part in the anti-social driving of motor vehicles involving two or more vehicles in a public place anywhere in the Leeds district.
“It carries a power of arrest and also forbids people from promoting, organising or publicising the anti-social driving of motor vehicles.
“I want to reassure people in the area that officers from the local neighbourhood policing team will be continue to monitor any issues and will take firm action to tackle any motorbike-releated anti-social behaviour.”
Anyone with information that could assist the investigation, particularly on those involved, is asked to contact officers via 101 quoting log number 362 of October 31 or call the independent charity Crimestoppers anonymously on 0800 555 111.
The Leeds Halloween rideout 2016
The incident had chilling echoes of the Halloween rideout in Leeds in 2016, when over 100 riders gathered on Kirkstall Road and drove into the city centre. Thirteen people were convicted and most given jail sentences for causing a public nuisance after driving in an anti-social and intimidating manner. Many were wearing Halloween masks. Police received over 160 calls from members of the public.
Organiser David Armitage, 26, from Headingley, claimed in court that he had arranged the event for charity and collected around Â£400 for the family of Sophie Smith, a Beeston teenager who was murdered by her boyfriend earlier that month. However, Sophie's family said they had never received any money and did not support the rideout.
The vehicles were seen speeding, weaving between traffic, riding on pavements, in bus lanes and on the wrong side of the road, going through red lights and no-entry signs and performing wheelies and other stunts. One group of riders drove through a narrow, pedestrianised shopping arcade in the city centre in a 'dangerous and reckless manner', with one quad bike colliding with a motorcycle and injuring the rider’s leg.
Similar 'rideout' events have taken place in cities across the country, and are normally advertised on Facebook.
There is no suggestion that last night's events were connected to the 2016 rideout. Police claim they have intervened and prevented further 'rideout' gatherings since the 2016 incident.