Gangs of bikers and youths pelting fireworks caused Halloween chaos for emergency services across the UK and Northern Ireland.
More than 200 motorcyclists gathered for a "Halloween ride out" in Solihull and Birmingham, while in Leeds a group of more than 50 racing off-road motorcycles and quad bikes brought Kirkstall Road to a standstill.
Police also faced trouble as fireworks were thrown at them in two separate attacks caught on video, with one officer narrowly avoiding being hit by an explosive in Tottenham, north London, the Metropolitan Police said.
Officers in Birmingham also tweeted footage of one of their vans being hit by a volley of fireworks.
There were similar scenes in Coalisland as fire crews came under attack from youths with fireworks, with hostile crowds forcing them to withdraw from incidents in Rostrevor and Newry, Northern Ireland Fire and Rescue Service said.
At least seven people were arrested and 10 motorcycles seized following the incident in Birmingham, West Midlands Police said.
The riders, many of whom were wearing face masks, caused "chaos" as they darted between traffic, jumped red lights and performed stunts on busy main roads.
At one point a police van came under attack, while the fire service also reported that a group of bikers were stopping them from responding to an emergency call.
West Midlands Police Chief Inspector Jack Hadley described it as "outrageous" and "totally unacceptable".
"This wasn't a rally of bike enthusiasts - this was loutish, criminal behaviour," he said.
"Bikers were riding without lights, at speed, dangerously, pulling wheelies in the street, mounting pavements and damaging vehicles."
Police closed Kirkstall Road in Leeds for 90 minutes as they waited for a gang of around 50 bikers to disperse following a similar incident.
Witness described the scenes as "utter chaos" and "madness" and compared them to those in the Mel Gibson film Mad Max.
A police helicopter attended the event, which is believed to have been organised on social media, but no arrests were made, a West Yorkshire Police spokesman said.
Scotland Yard said one youth had been detained in relation to an attack on police in Tottenham, north London.
Footage from the dashboard camera of a car being driven by neighbourhood watch group Shomrim showed a firework fly past a running Metropolitan Police officer.
The rocket then ricocheted and exploded next to a police car in Fladbury Road at around 9.40pm.
MPS Haringey tweeted: "Our officers responding to #ASB fireworks related call, some youths decided to aim at us instead!! No officers injured."
West Midlands Police also tweeted footage of a police van repeatedly being hit by fireworks being launched from Balsall Heath Park in Birmingham.
West Midlands Police said one teenager had been detained following the incident on Taunton Road at around 8.30pm on October 22.
The 16-year-old boy, who was arrested on suspicion of public order offences and criminal damage on October 26, has been released on bail, a spokesman said.
Another 16-year-old boy has been referred to the police's youth offending team.
Sergeant Andrew Lewis, from Sparkbrook, said: "This was totally irresponsible behaviour. I believe that a group of youths specifically targeted the police.
"Fortunately no-one was hurt but we could have so easily been dealing with something far more serious."
Police were also targeted as they attempted to disperse a crowd of around 100 youths in Cheshunt, Hertfordshire, on Monday night.
The group threw fireworks at officers, parked cars and houses in the Rosedale and Andrews Lane areas of the town, Hertfordshire Police said.
Some 40 officers attended the incident, which took several hours to defuse, and a number of arrests were made, a spokesman said.