People campaigning to save a historic bridge in Leicester have vowed to take "direct action" when the bulldozers move in to demolish the landmark.

The Bowstring Bridge protesters would not say exactly what form the action would take, but said the contractors who carry out the work should not expect an easy ride.

Demolition of the landmark is due to begin on or about Monday, September 21.

Campaigner Lee Mullen set up a Facebook group opposing the demolition of the bridge, and the neighbouring Pump and Tap pub, which has been joined by 3,000 people.

He said he was expecting protests at the site on the day workmen moved in.

Mr Mullen said: "We will e-mail councillors for what it is worth but it will be a case of taking direct action – although whatever we do will be peaceful.

"We have tried to get in touch with the demolition contractors to warn them that it is a sensitive issue and it may not be as easy for them as other demolitions. They are going to be extremely unpopular."

About 250 protesters gathered at Bede Park on Saturday. Many insisted that while the bridge was still standing they would not give up their fight or relinquish hope.

Leaflets with the email addresses of city council leader Ross Willmott and cabinet member for regeneration Patrick Kitterick were circulated, and people urged to tell the councillors why they believed the demolition should not go ahead.

Video from Citizens' Eye

Campaigner Sheila Smith, 85, of Rowley Fields, was taking part in her first protest rally. She said: "All my life I have never done anything like this, but I am so incensed I feel I have to. I was born in New Parks Street near the bridge and grew up there, so it means an awful lot to me."

Councillor David Bill, chairman of Hinckley and Bosworth Borough Council, told the crowd that the action of residents was the only hope for preserving the city's heritage.

He said: "We do not seem to have anyone at national level who is prepared to speak up for our heritage, so it is only people like you, at local level, who can make a difference."

Members of the crowd held up placards declaring "LCC Don't Care About Residents" and "Save Our Bridge".

Many described the plans – which will allow for a new De Montfort University sports centre – as "cultural vandalism" and said they believed other alternatives had not been given enough consideration.

Laura Elvin, 22, who lives nearby in Wilberforce Road, said: "There are areas in the city that are derelict, disused and ugly – why knock down something that actually gives character to the area?"

Friend Robert Knight, 28, of Bede Street, said: "It is an uphill struggle, but we will be writing e-mails to the councillors and keep on doing what we can to help."

Chris Martin, of Raymond Road, said: "If, on the day, there is a way of protesting that is legal and safe then I will be there.''

One of the rally organisers, Stuart Simmonds, 37, of New Parks, Leicester, said the turnout demonstrated the strength of feeling behind the campaign to save the bridge and the pub.

He said: "It just shows how much people care. We will carry on protesting for as long as the bridge and pub are still up."

On Saturday evening about 40 people staged an impromptu protest on the bridge with banners. One said: "We didn't plan this. It was just spontaneous. We'd all been to the protest at Bede Park and wanted to let people know how we felt about the council's disgusting plans to knock down the bridge."

Inspector Bill Knopp, of Leicestershire police, climbed up to talk to the group. He described the protest as peaceful.

Insp Knopp said: "Once we realised what was going on our main concern was to make sure everyone was safe. None of the protesters were being violent or aggressive. There was quite a friendly atmosphere up there."

Councillor Willmott said he had sympathy with the protesters but said a decision had already been made.

He said: "Obviously some people feel strongly about the bridge and I understand that. The decision on the bridge was not one taken lightly and it was supported by all three main political parties.

"It will cost millions to keep the bridge and make it safe. Back in 2004 I said if someone wanted to keep the bridge and move it they could but no one has come forward. It's not likely things will change but I respect people's strong feelings."