He has no special interest in science fiction, but the creator of a Swedish sci-fi drama that pits robots against humans has struck a nerve among viewers.

"Real Humans", by screenwriter-actor Lars Lundstroem, stars humanoids called "hubots", a word mixing humans and robots. They are merchandise, bought and sold, run on electricity, but can think, make choices, have sex with humans, even fight for their own freedom and rights.

Their owners want to keep them in their place as docile, high-tech consumer products, be it servants, workers, sex partners, even replacements for lost family members.

Other people, a political movement called "Real Humans", feel all has gone too far. They want to return to a society without hubots.

For Lundstroem, "the main premise in 'Real Humans' is: what is a human being?"

The lines between real and robot are deliberately blurred to ask: is it possible to build a human? What is a soul? Are we just some kind of biological machines?

"It is a tough question to answer, almost impossible, and it is very rare we are confronted with questions about the kind of creatures we are," he told AFP.

The series, set in a parallel, modern-day Sweden, came out in 2012 and was quickly bought up in more than 50 countries from France to South Korea to Australia.

It also caught the eye of American xBox Entertainment Studios and Britain's Channel 4 who are developing an English-language adaptation called "Humans" set to premier in 2015, according to the entertainment bible Variety.

Lundstroem cannot even remember how he came up with the idea.

"Maybe it was after seeing one of those human-like robots they have made in Japan, but I really don't know," he told AFP.

"I just thought it was a great starting point for a drama series, something that could generate a lot of story."

The show is chock full of action, intrigue and romance: programmers breaching legal protocols to make the hubots even more human-like, others -- derided as "hubbies" -- breaking taboos on having sex with hubots.

Lundstroem's plots are less science-driven than metaphors for contemporary social issues -- prejudice, minorities, immigration, slavery, relationships.

It's been described as everything from creepy to startling to superb sci-fi.

"This Swedish show about an abducted sex robot is creepy as hell," sci-fi expert Charlie Jane Anders said in December 2012, adding that it was both "beautiful" and "disturbing looking".

Some critics have said that what makes the series scary is that the hubots are so similar to human beings.

In the show, household robot Mimi almost becomes a new member of the Engman family.

While the son falls in love with her, his sister starts to fear that the mother likes Mimi better than her.

"One reason why people could find the show scary is that it presents a future where robots are so similar to humans that they could end up replacing people," Swedish TV critic Rosemari Soedergren said.

"People have always had some kind of fear and suspicion about technology and machines."

- 'So mentally tired' -

Lundstroem admits he has no experience in the genre.

"I have consciously not consumed a lot of science fiction, because I was afraid I could be influenced by it," he said. "I saw my lack of background as a strength."

The show premiered on Sweden's public broadcaster SVT in 2012 and has run two seasons. Lundstroem said production costs are high and though he's working on a third season, he has faced difficulty in finding financing.

The same fine line between humans and hubots that sparked Lundstroem's interest became a challenge for the actors.

Those playing hubots have won praise but it was surprisingly exhausting, said Lisette Pagler who portrays Mimi, one of the more developed robots in Real Humans.

"We had to deal with tiny, tiny nuances," she said. "If it was too machine-like, the dialogue became uninteresting, and if it was too human, we were not credible as robots.

Mime artists were brought in to teach them how to control their movements.

We "didn't realise how frustrating it can be to remove all the human tics we have, to control them all the time. You need to be aware of when you blink, you can't scratch yourself, you can't make quick movements.

"I had never been so mentally tired after doing so little physical effort," she said.

"Sometimes we modified their voices, but it was mainly little noises and sounds and ticks which were really helpful in creating the illusion," Lundstroem said.

His team interviewed a robotics researcher at Stockholm's prestigious Royal Institute of Technology for help, but "we couldn't use any of it."

"Technology hasn't come as far as it had in our series, there is no science to rely on," he said. "We only had our fantasy to imagine what would happen if something like that were invented and began to be sold to people.

"But that's also what made it exciting," he said.