A ZOMBIE march through the streets of Bristol could be cancelled next year after a few "mindless idiots" hijacked part of this year's event.

More than a thousand people descended on the city centre on Saturday for the march, in which people dressed in zombie costumes, such as ghoulish chefs and "undead" police officers, nurses and convicts for post-apocalyptic shuffle from Stokes Croft to Castle Park.

But the fun event was marred when a few people threw fireworks among the walkers as they went under St James Barton roundabout.

There were also reports that people had climbed on to a police van. Organisers now fear they will not get permission to run the event again.

Rhiannon Roberts, who has organised the event for the last five years through Facebook, left a strongly-word message on the social networking site for those responsible for the disruption.

She said: "Hello zombies. This statement is for the people who set off fireworks in the crowd (I know who you are, by the way), the person who climbed on the police van, and all of the people that joined in after.

"Because of you, that's it. It is over. We will not be able to do this next year. We had large scale plans for next year, but we will never get permission for it now.

"On multiple occasions it has been stated that this walk was not a political movement, we are not trying to change people's minds, we are zombies. We wanted fun, only fun. It was only ever about fun.

"Thanks to all the genuine zombies that made the event mostly awesome. And thank you to the few idiots that messed it up for the rest of us."

People came from all over the country to take part in the march, which at 3.30pm set off from King Square under St James Barton roundabout, through Broadmead to Castle Park.

Messages of support for the event were left on Facebook.

Paul Williams said: "Don't give up on it. I am sure the authorities would want to encourage such a fun and creative event to happen in Bristol."

Other people on the march said zombies taking part had cleared up any mess along the way.

A poster calling herself Vonalina Cake said: "I saw a couple of minor things that got sorted by zombies and others on the route – smashed glass, dropped litter – a mostly brilliant group. It's a great event and always goes off without a bang, so I hope this will not mar it."

But others were upset the event was hijacked. Jonah Davies said: "I don't think I could pick up my bat again in good conscience knowing there could now be foolish people out there that would risk other people's safety like they did with incidents with the firework and the police vans."

James Langlands, 29, inset left, a project manager from Clifton, went to the march with a group of friends.

He said: "The atmosphere was terrific. Bystanders were taking it in good spirits and everyone had a smile on their face. I saw dozens of people with cameras out and taking photos. People were playing up to the cameras, and it all seemed very good-natured. I only saw one policeman the whole time, and there was no noticeable police presence. I didn't see a thing, and I was surprised to hear about the problems. It was getting a bit boisterous outside the Tesco in Broadmead, but there was certainly nothing malicious.

"Everyone was excited by the whole thing. I didn't see anyone put off by it or upset, and it was all good-natured. It is a crying shame if it doesn't happen next year. It is the same old story – a few clowns who spoil it for those who want to have a bit of harmless fun."

Police said the disruption was caused by people not associated with the march. Spokesman Martin Dunscombe said: "This is traditionally a well-organised, fun and peaceful event. It is well stewarded and this year the walk was from King Square to Castle Park. At about 4pm police were made aware that a small number of people had sprayed some sort of liquid on some shops in Broadmead and let off fireworks in the St James Barton underpass. It is clear this behaviour was committed by a small minority of activists not associated with the event and intent on using the march as cover for their disruptive and anti-social behaviour.

"Those people taking part in the march made efforts to distance themselves from the troublemakers.

"Organisers of the event are not required to consult police on the plans but we would welcome the chance to have a conversation with them beforehand to make sure the event is safe and enjoyable."

A spokesman for Bristol City Council said the authority had no role in monitoring or licensing the event.