LOS ANGELES • Taylor Swift and Tom Hiddleston have made their official Instagram debut as a couple, in a photo posted on the social media platform.

Britany Maack, Swift's childhood friend, posted the picture of the cuddling couple sitting alongside two other couples - married actors Blake Lively and Ryan Reynolds, and Maack herself with husband Ben LaManna.

Maack captioned it simply as "Us". According to reports, it was taken after they celebrated the United States' Independence Day over the weekend at Swift's seaside Rhode Island home with friends including models Cara Delevingne, Gigi Hadid, Karlie Kloss and actress Ruby Rose.

Hiddleswift, as the couple are dubbed, have kept people guessing about their relationship since the first photos of them, also on a Rhode Island beach, appeared in The Sun tabloid last month.

On Sunday, they were seen in paparazzi pictures frolicking together in the Atlantic Ocean while celebrating the Fourth of July.

In one photo, the American singer was pictured grabbing and kissing her alleged British beau, 35. He was wearing a "I (Heart) T. S." tank top, reported Us Weekly magazine. On his arm was a heart-shaped temporary tattoo with "T" on it.

Swift, 26, is known for her huge, celebrity-packed Fourth of July parties. This year, her friends sported matching swimsuits in red, white and blue.

On Monday, the merry-makers had fun in her garden on an inflatable, red-white-blue slide with the words "Taymerica" on the side. They also played football before ending the holiday with a fireworks display.

Meanwhile, it was reported that Swift's fans in China have been stopped from betting on a Hiddleswift split.

Xinhua news agency last week reported that the fans had been buying insurance to hedge against that probability. As noted by the Washington Post, the odds were favourable, given Swift's habit of using her ex-boyfriends as fodder for vengeful, chart-topping pop songs. Swift had very brief romances with her past boyfriends, such as singers Joe Jonas and John Mayer.

Bookies on Taobao, China's online marketplace, offered to give bettors twice their money back if Hiddleswift called it quits within the year. Hundreds of fans took up the deal.

"These stars break up all the time, which gives us the opportunity to earn a lot of money," said one buyer, according to Xinhua.

However, Taobao later shut down the practice, calling it a form of gambling, which is illegal in China.