Bella Hadid's alleged stalker has been arrested.

Bella Hadid

Bella Hadid

The 21-year-old model contacted police after she noticed a man had posted a photo of her apartment building online, and he was arrested shortly after she made the call to emergency services.

According to TMZ, police believe the 37-year-old suspect is the same man who has been sending messages to Bella, in which he threatened her and her family, since December.

The unnamed person has been booked for aggravated harassment and stalking and is currently still being held in custody.

Meanwhile, Bella's older sister, fellow model Gigi Hadid, recently spoke of how protective she feels towards the brunette beauty.

She said: "She's one of the only people I'll get aggressive for. She makes me so proud. I would do anything for her."

And Bella has previously declared her sister to be her "best friend" and knows she can always rely on her for help, support, and career advice.

She explained: "Gigi is my best friend and I love her to death. She's been through everything I'm going through now because she's been in the business longer.

"If I'm sad I'll call her and she always makes me happy again. She's the best, I love her."

And Bella has admitted to finding it much harder to cope with being in the spotlight than her sister has.

She said: "My sister is very bubbly and very out there, and I was always very reserved.

"I would literally start crying and shaking if I had to do interviews at red carpet events. It was really nerve-racking and it's scary.

"It gets a lot better once you have to talk to people every day. Then you're like, 'OK, I guess it's my job, I have to do it!' "