Science-fiction television series "Westworld" has been cancelled by American network HBO, reported entertainment trade Deadline on Friday.

It said the main cast – which includes actresses Evan Rachel Wood and Thandiwe Newton – will be paid for a fifth season, even though it will not be produced.

The salaries they would be owed for the fifth season are believed to be US$10 million (S$14 million) to US$15 million in total.

The cancellation was reportedly due to the show's declining ratings over its four seasons aired to date. It comes on the back of aggressive cost-saving measures by HBO's parent company, Warner Bros Discovery, which included shelving the "Batgirl" film for streaming service HBO Max, even though it was already in post-production.

The company had reported a quarterly loss of US$2.3 billion on Thursday.

"Westworld" was created by married couple Jonathan Nolan – brother of film-maker Christopher Nolan – and Lisa Joy. The dystopian series centres on a futuristic amusement park staffed by robots, which soon begin to malfunction.

On Instagram, Jonathan Nolan and Joy shared a statement attributed to their production company, Kilter Films.

"Making 'Westworld' has been one of the highlights of our careers... We've been privileged to tell these stories about the future of consciousness – both human and beyond – in the brief window of time before our (artifical intelligence) overlords forbid us from doing so," read the statement.

The couple's much-anticipated follow-up to "Westworld", The Peripheral, is now streaming on Prime Video. It is thematically similar to "Westworld", exploring a near future in which computer simulations and virtual worlds are much harder to distinguish from reality. It stars Chloe Grace Moretz, who shot to fame with superhero comedy "Kick-Ass" (2010).