Australia's Nick Kyrgios withdrew from the Estoril claycourt tournament on Friday following the death of his grandfather, the world number 16 announced on Twitter.

Kyrgios, who was due to be top seed at the Portuguese event starting on Monday, said he was heading home to attend the funeral of his grandfather Christos Kyrgios who lost his battle against cancer.

"I have unfortunately withdrawn from the Estoril Open to go back to Australia and attend my grandfather's funeral," said the controversial 22-year-old.

"The decision was a hard one but my family is very important to me and I feel the need to be around my loved ones at this time as well as pay my respects to my 'Papou' who I loved very much."