Football fans attending Liverpool's crunch Champions League game at Anfield were today warned the use of flares inside or near the stadium could lead to jail.
Police issued advice to supporters going to the last-16 match tonight, informing them of a major officer presence in the city.
And the force was keen to warn anyone considering bringing flares or pyrotechnics to the game could face strong action.
The practice was described as "reckless and dangerous" by police.
Plain-clothed and uniformed officers will be deployed at Anfield as thousands of Liverpool and Spanish fans flock to the stadium.
Mounted police will patrol the ground and the helicopter will be keeping a close eye on proceedings from above.
Fans without tickets for the crucial second leg, which Liverpool trial 1-0 after a rare defeat in Madrid, were specifically advised to stay away from the stadium.
In a statement, Match Commander Superintendent Dave Charnock said: “We’re pleased to welcome fans of both clubs to what promises to be a fantastic night in the city.
"As with all major games fixtures at Anfield, we will have officers on duty at the ground, both uniformed and plain clothed, and specialist resources including mounted police and the National Police Air Service (NPAS).
"We will also have a city centre policing plan in place throughout the day.
"This is standard procedure with the safe and smooth movements of fans in mind.
"Merseyside Police, Liverpool FC, Liverpool City Council and our travel partners will also be sharing advice and information in the lead up to the game, to assist people travelling by road, rail, bus and other means.
"You can follow our social media accounts to keep up-to-date.
"We know that this will be a busy operation and we hope that fans attending the match will act as ambassadors for their clubs.
"While recognising that some supporters feel they can add to the atmosphere of the occasion, the use of flares and other pyrotechnics at and around football matches is a concern.
"We fully support the club in working to eradicate this dangerous and reckless practice and would ask that supporters work with us.
"The police and courts take these offences very seriously and prosecution can result in a prison sentence.
"I would remind people that this can apply not only within the stadium, but also in the surrounding streets and when attempting to enter the ground.
"Merseyside Police is committed to ensuring that everyone involved and attending the game tonight has a safe and enjoyable experience and we will not tolerate any criminal, or anti-social behaviour.
"As usual we would ask fans with tickets to arrive at the ground as early as possible.
"Fans without tickets should not attend at all; they will not be allowed entry into the stadium."
The match kicks off at 8pm.
