Kim Kardashian was "inseparable" from husband Kris Humphries as she celebrated her 31st birthday this weekend.

The socialite - who has been married to the basketball star for two months - spent a whirlwind two days marking the occasion in both New York and Las Vegas.

Joined by her older sister Kourtney and her boyfriend Scott Disick on the New York leg of the celebrations, Kim and Kris appeared "unfazed" about rumours their marriage was in trouble after the sportsman was seen without his wedding ring.

An onlooker at the city's The Darby restaurant told the New York Daily News newspaper: "They were sitting next to each other, kissing a lot. They were unfazed by the rumours."

In addition to enjoying a special cake to mark the occasion, the couple were treated to an impromptu performance by fellow diner Pink, who took to the stage to perform a rendition of 'Killing Me Softly'.

Meanwhile, on Saturday (22.10.11), the pair partied alongside Khloe Kardashian and her husband Lamar Odom and Kim's mother Kris Jenner at Las Vegas' Cosmopolitan Hotel, where they were treated to a sports car-shaped cake that featured dolls of the couple at the wheel.

However, the night was not without drama, and Kris Jenner was forced to tell off her son-in-law when he started knocking on random doors of the hotel as a joke.

A source said: "Kris was trying to move him along but Kim found it funny for a minute."