Demi Lovato is ''humbled'' by the support she's received following her dad's death.

The 'Heart Attack' singer has thanked her fans and friends including 'X Factor' co-star Simon Cowell for their condolences after her estranged father Patrick Lovato passed away last week.

Demi wrote on Twitter: ''I feel so humbled to have had so much support from my fans, friends, family and complete strangers.. God bless you all, thank you so much ❤ (sic)''

The 20-year-old star cancelled a planned photoshoot with her fellow 'X Factor' judges Simon, Kelly Rowland and Paulina Rubio on Saturday (22.06.13) in order to grieve her dad's death - news of which was first broken by her older sister, Dallas, over the weekend.

Demi's sibling wrote on Twitter: ''Rest in peace daddy I love you... (sic)''

Simon, 53, and Paulina, 42, were among the first stars to pay their respects to Demi during her time of need.

Simon tweeted: ''My thoughts are with you Demi. X''

Paula wrote: ''lov u lil sis my prayers r w u guys! Te amo @ddlovato sorry for ur loss, i know what it feels Nothing we can say it's enough... (sic)''

Demi, who was raised by her mother Dianna and her stepfather, Eddie De La Garza, has previously opened up about her strained relationship with Patrick.

In 2011, she penned a song about him, 'For the Love of a Daughter', and in 2009 the singer-and-actress revealed she hadn't spoken to her biological father in ''two years''.

She said: ''The last time I talked to him was two years ago. You try to have faith in somebody, even when you're the last person that believes in him. But when somebody lets you down after you've been the only one there for them, and so many times, you don't know what else to do. I had to cut off all connection. It was hurting me too much.''

Patrick had reportedly been suffering with cancer in the final years of his life.