Firefighters in England and Wales staged a fresh strike tonight in their bitter row with the Government over pensions, disrupting firework displays.
Members of the Fire Brigades Union (FBU) walked out at 6.30pm, mounting picket lines outside fire stations until the stoppage ends at 11pm.
A further two-hour strike will be held from 6am on Monday, the day before Bonfire Night.
In London, all striking FBU staff who would normally be on duty were recalled to their stations because of a major blaze at a scrap metal yard in Dagenham.
London Fire Brigade (LFB) said this was under the agreed "Recall to Duty Procedure" and was voluntary.
Fire brigades across the country urged members of the public to put off any firework displays in their own gardens tonight and to switch them to Saturday or go to an organised event.
The union held a four-hour stoppage last month but called off another strike after it appeared a deal was in sight, but officials said the Government and fire employers had failed to offer any firm guarantees on jobs or pensions as a result of changing the pension age from 55 to 60.
The union fears firefighters will be made redundant if they fail fitness tests and are unable to find other work in the fire service.
FBU general secretary Matt Wrack said: "It is ludicrous that after two years of negotiations the Government has still not sorted out this mess.
"Firefighters are keen for these issues to be resolved through discussion but the Government won't even listen to its own evidence which highlights that the schemes are unworkable and unaffordable.
"Firefighters want a pension scheme that takes account of the hazardous nature of the job, is affordable and workable for them and for the taxpayer. We hope this brief strike will mean the Government returns to negotiations so we can agree a sensible way forward."
The FBU said it has timed the strikes so that celebrations on Bonfire Night and the Saturdays before and after November 5, which are the most popular times for firework displays, can take place.
The union said it was led to believe that the Government was willing to offer a guarantee that firefighters whose fitness levels declined with age would not face being sacked, adding that fire service employers had confirmed that this risk does exist for firefighters under the new arrangements.
Negotiations with the Scottish Government have so far prevented any industrial action taking place, although a final settlement is yet to be reached on all the issues in the dispute.
LFB said today was likely to be one of the busiest days of the year for the fire service, ahead of Guy Fawkes Night and Diwali celebrations.
London Fire Commissioner Ron Dobson said: "Fireworks cause serious fires each year and bonfires can quickly get out of control, which is why we're urging people to attend organised displays.
"During the strike we will have a contingency fire and rescue service of 27 fire engines, crewed by temporary firefighters. Serious emergencies will be attended, but smaller incidents won't so we are calling on the public not to put themselves at risk by lighting fireworks and bonfires."
South Yorkshire Fire and Rescue said its emergency response service will be "severely reduced" because of the strike.
Chief Fire Officer James Courtney said: "Don't hold your bonfire or fireworks display tonight.
"We're satisfied with the contingency arrangements we are putting in place, but our 999 service will still be severely depleted so we need the public to help keep our fire engines available for real emergencies."
Fire Minister Brandon Lewis said: "This strike action by the FBU is completely unnecessary and does nothing but damage the good reputation firefighters have with the public.
"We offered firefighters similar fitness principles to those the FBU accepted in Scotland. The FBU should reconsider their decision to strike - announced just four days into discussions - and work for a resolution to this dispute.
"The public will be baffled by the FBU's course of action when they hear that the deal being offered to firefighters gives them one of the most generous pension schemes in all the public sector.
"A firefighter who earns £29,000, and retires after a full career aged 60, will get a £19,000-a-year pension, rising to £26,000 with the state pension. An equivalent private pension pot would be worth over half a million pounds and require firefighters to contribute twice as much."
The union has disputed the figures.
Shadow local government and communities secretary Hilary Benn said: "This strike is a sign of the Government's failure to get round the table and sort this dispute out. It has had two years to do so and it is time ministers did their job.
"As we all know, firefighters do a dangerous job which the public greatly values and as they get older they need to have the fitness necessary to fight fires. That is in the interests of both firefighters and the public, and safety must be the first consideration.
"It is not responsible, however, to have chosen to take action on a weekend when, because of Bonfire Night and Diwali celebrations, there is an increased risk to the public. That's why the FBU called off their strike three years ago at this time of the year because of safety concerns."
Twenty fire engines and 120 firefighters and officers were attending the blaze at the yard in Perry Road, Dagenham.
Around 1,500 tonnes of scrap metal in the open air was alight. Cylinders were believed to be involved and a hazard zone was put in place as some cylinders can explode when exposed to heat. The smoke could be seen from miles around.
An LFB spokesman said: "There is a lot of smoke in the local area and we're asking residents to close their doors and windows."
The Brigade was called at 3.19pm. The cause of the blaze is not yet known.
Scotland Yard said police officers and ambulance crews were also at the scene.
"Local road closures are in place and motorists are advised to avoid the area if at all possible," a spokesman said. "The A13 remains open at this time but may have to be closed if conditions change."
There were no reported injuries.
London Mayor Boris Johnson said: "Londoners will rightly want to see the major incident in Dagenham this evening brought to a speedy and safe conclusion.
"I fully support the Fire Commissioner's decision to recall all striking FBU staff who would normally be on duty and I would urge London's dedicated firefighters to do their utmost to help to bring this fire under control."
Mr Dobson said later: "The large fire in Dagenham is ongoing and has been declared a major incident.
"We have issued a recall notice and are asking striking Fire Brigades Union members in London to carry on working.
"The FBU have told firefighters not to follow the recall notice. They claim the recall is not valid because there is no risk to life. There is no reference to risk of life in the agreed protocols to implement a major incident.
"A major incident can and has been implemented because of the size of this fire and the resources needed to deal with it. By not responding to the recall it is the FBU that is in breach of the agreement."
No-one from the FBU was available to comment.
Mr Lewis said later: "I'm pleased to see contingency plans across the country are working well so far tonight.
"Even in London, where the FBU have disappointingly breached the return to work protocol for a major incident, contingency plans have continued to keep the public safe.
"I'd like to thank all whole-time and retained firefighters and volunteers who have remained on duty tonight."
FBU London Secretary Paul Embery said :"There has been no recall of firefighters agreed with the Fire Brigades Union in London.
"Unless this changes, firefighters will therefore continue to respect the strike action until 11pm tonight.
"The London Fire Brigade has been giving assurances that their contingencies were sufficient."