Workers at five UK McDonald's restaurants have walked out on strike in a dispute over pay and union recognition.
Staff in Manchester, Cambridge, Crayford, south-east London, and two branches in Watford, formed picket lines as part of the action.
The Bakers, Food and Allied Workers Union is seeking formal recognition from the US fast food giant as well as campaigning for a £10-an-hour minimum wage and an end to lower rates for younger workers.
A union spokesman said members of the public, trade unionists, Labour Party members and others have been offering support to the strikers.
Lewis Baker, a McDonald's worker from Crayford, said: "Every message of support builds our confidence as we demand a fair wage and respect for the job."
Annalise Peters, who work at McDonald's in Cambridge, said: "The public and the labour movement have given us so much support and encouragement. When we went on strike last September it felt like a new workers' movement was being born."
Paul Pomroy, chief executive of McDonald's UK, said none of the affected stores would close, pointing out that only 11 workers out of a total of 120,000 were involved in the action.
He added that he prided himself on listening to staff, saying: "We survey them twice a year, and have recently increased the starting pay rate, giving the biggest increase to younger workers."
The union said more than 11 workers were taking action.
Richard, a striking @McDonalds worker in Watford, stands outside his store and tells bosses: “You cannot belittle us. We are part of the trade union movement and we will win!”May 1, 2018
A McDonald's spokesman said: "We are expecting industrial action outside five of our restaurants today. With three strikes scheduled to take place this morning, we can confirm that across these three restaurants only one person who was scheduled to work took industrial action and this was in Manchester. Other attendees, at Cambridge and Crayford, were protesters and not our employees on strike.
"While we are disappointed, given our focus on putting people at the heart of our business, we are reassured that the number of our people involved is very low and an extremely small proportion of our UK workforce of 120,000.
"It is also regrettable that, during this process, we have had reports of intimidation of our people from activists. That is not behaviour we tolerate under any circumstances and we intend to investigate this further.
"We take the interests and well-being of our people very seriously and encourage anyone to speak up if they ever have any concerns.
"Our people can talk to our managers and raise issues informally, or more formally through our grievance procedure, and this is our preferred route to dealing with issues relating to our workforce. We remain committed to our people and their well-being at work.
"The intended strike action relates to pay and contracts. Over the last three years, we have taken a number of additional steps to ensure McDonald's UK remains a great place to work.
"Since September 2015, we have made three significant pay moves, and to maintain the many benefits we offer, from the great training and development opportunities, to payment of overnight premiums, which so many businesses have taken from their people in recent times.
"As promised last year, everyone has now been offered a minimum guaranteed hours contract. Despite this, around 80% of our people have selected to stay on flexible contracts because they value the opportunity to fit their work around their other commitments."
UK shadow chancellor John McDonnell has written to McDonald's chief executive Steve Easterbrook saying the workers' demands were "fair and reasonable" and suggesting a meeting to discuss issues such as pay and union recognition at the company.
He said: "I believe that every worker deserves what they are calling for - a real living wage of at least £10 an hour, security in work and a choice of fixed hours, the right not to be discriminated against on the basis of age, and the right to form a trade union and for that union to be recognised by the company.
"Under a Labour government, all workers will be entitled to a real living wage of at least £10 an hour, an end to zero-hour contracts, an end to the unjust youth minimum wage rate, and powers for unions to support workers who wish to form a union.
"It is not too late to address the problems your workers have raised and to secure a reputation for your company as a good employer."