A majority of employees at a US Apple store have voted to form the tech giant's first union, in the wake of similar unionisation drives at Starbucks and Amazon locations.

Of the 110 employees at the Towson, Maryland shop, 65 voted in favour and 33 against, according to a live count broadcast on Saturday by the federal agency overseeing the vote.

The vote comes after a group of employees called AppleCore (Coalition of Organised Retail Employees) campaigned for unionisation, demanding a say in deciding on wages, hours and safety measures.

"We did it Towson! We won our union vote! Thanks to all who worked so hard and all who supported! Now we celebrate... Tomorrow we keep organising," AppleCore tweeted.

Saturday's result means that the shop's employees, who have been voting since Wednesday, should form their own branch of the International Association of Machinists and Aerospace Workers (IAM) union, once the agency has certified the results.

Saturday's vote result follows several symbolic victories – including among workers for giants such as Amazon and Starbucks – by the country's unions, on the decline for decades, to which President Joe Biden has lent his support.

It was not the first time employees at an Apple store have tried to unionise, but it was the first attempt that resulted in a vote.

Apple's director of distribution and human resources, Deirdre O'Brien, visited the shop in May to address employees.

"I want to start out by saying it's your right to join a union, but it's equally your right not to join a union," O'Brien said, according to audio published by Vice.

"If you're faced with that decision, I want to encourage you to consult a wide range of people and sources to understand what it could be like to work at Apple under a collective bargaining agreement."

The presence of an intermediary would complicate relations between Apple and its employees, she said.

"I'm worried about what it would mean to put another organisation in the middle of our relationship, an organisation that does not have a deep understanding of Apple or our business," O'Brien said.

"And most importantly, one that I do not believe shares our commitment to you."

The vote comes in wake of a broader unionisation push at some of the United States' biggest companies.

After a union was formed at two Starbucks coffee shops in December in the northern city of Buffalo, employees at more than 160 of the chain's locations have filed for similar votes.

At Amazon, employees at a New York warehouse surprised everyone in early April by voting overwhelmingly to form a union, a first for the online retail colossus in the United States.

But the company has asked for the result to be cancelled and a second vote to be held.

Apple declined to comment on the vote in Maryland.

The IAM union slammed the Silicon Valley giant's efforts to discourage employees from voting yes.

A video from the group, released by pro-union media outlet More Perfect Union, shows AppleCore supporters in Maryland accusing the company of "union-busting" tactics, including "intimidation," which the employees called "disgusting."

IAM International President Robert Martinez Jr said he applauded the workers' "courage."

"They made a huge sacrifice for thousands of Apple employees across the nation who had all eyes on this election," he said in a statement. "I ask Apple CEO Tim Cook to respect the election results and fast-track a first contract for the dedicated IAM Core Apple employees in Towson."

"This victory shows the growing demand for unions at Apple stores and different industries across our nation." (AFP)