NEW YORK — Labor organizers turned up the pressure on McDonald’s and other fast-food chains to raise worker pay on Thursday, with plans to stage actions in more than 30 countries.

The demonstrations build on a campaign by unions to bring attention to the plight of low-wage workers and get the public behind the idea of a $15-an-hour wage.

Industry groups say such pay hikes would hurt their ability to create jobs and note that many of the participants are not workers. The protests are being backed by the Service Employees International Union and began in New York City in late 2012. Since then, organizers have steadily ramped up actions to keep the issue in the spotlight.

In March, for instance, lawsuits filed in three states accused McDonald’s of denying breaks and engaging in other practices that deprive employees of their rightful pay. Workers were referred to lawyers by union organizers, who announced protests over “wage theft” the following week.

Organizers say workers went on strike in 150 U.S. cities on Thursday, including 20 at a restaurant in St. Louis that had to temporarily close as a result.

In Denmark, McDonald’s worker Louise Marie Rantzau said a collective agreement with McDonald’s in the country prevents workers from protesting the chain. Rantzau, who earns about $21 an hour under the agreement, said she and others planned to demonstrate outside Burger King or other restaurants and post photos on social media.

Images on social media showed workers demonstrating in places including Dublin and Sao Paulo, Brazil.

In New York City, a couple hundred demonstrators beat drums, blew whistles and chanted in the rain outside a Domino’s for about a half hour. Among those who took turns speaking were local lawmakers, community leaders and fast-food workers.

“Corporations are able to make money — millions and billions of dollars. We should be able to make a decent salary so we can take care of our families,” said Sheila Brown, a mother of four who works at a KFC.

Although many customers say they’re not aware of the ongoing actions, the campaign has captured national media attention at a time when the income gap between the rich and poor has widened and executive pay packages have come under greater scrutiny.

The current rate of $7.25 an hour translates to about $15,000 a year, assuming a person works 40 hours a week.

Still, fast-food workers have historically been considered difficult to unionize, since many are part-timers who don’t stay on the job for long. But supporters say that is changing, with more people relying on such jobs to support families. Last week, workers and union representatives from countries including Argentina, China, El Salvador, France, Ireland and the United Kingdom met in New York City to strategize for the day of global actions.

The National Restaurant Association called the actions “nothing more than big labor’s attempt to push their own agenda.”