Zac Efron has thanked fans for their ''support'' after it was reported he went to rehab earlier this year.

The '17 Again' actor sought treatment for alleged cocaine and alcohol addiction, and he has finally broken his silence in a grateful message to fans, hinting at a tough ''few weeks''.

He wrote on Instagram: ''Hey guys! Just returned from an incredible trip to Peru with my dad and wanted to thank you all for your support these past few weeks ... means the world to me. Love you guys! - Z''

The star also posted a photograph of himself looking healthy with Machu Picchu, Peru in the background.

While Zac, 25, still hasn't directly referred to the reports, fellow stars - including his 'Parkland' co-star Marcia Gay Harden - have praised him for seeking help.

Marcia previously said: ''In my opinion, Zac Efron is a total hero. Him seeking help encourages other people with addictive issues to seek help. It's brave of him.

''I think only a coward lives in denial, and he is not a coward. He's a hardworking go-getter and I love him.''

Meanwhile, friend Rob Lowe defended his decision to enter rehab, insisting he must be ''serious about [his] recovery'' if his issues were kept quiet until after he'd left the treatment centre.

He tweeted: ''A thought: if you only find out a person has been to rehab weeks or months after they got out, they're probably serious about recovery.''