It has grossed more than $1.3bn (£800m) worldwide, wowed the critics, and spawned a new generation of fans, the so-called Avatards, who have taken to painting their faces blue.

But the film director James Cameron was facing claims today that his 3D blockbuster Avatar owes an unacknowledged debt to the popular Soviet fantasy writers Arkady and Boris Strugatsky.

Cinema audiences in Russia have been quick to point out that Avatar has elements in common with The World of Noon, or Noon Universe, a cycle of 10 bestselling science fiction novels written by the Strugatskys in the mid-1960s.

It was the Strugatskys who came up with the planet Pandora – the same name chosen by Cameron for the similarly green and lushly forested planet used as the spectacular backdrop to Avatar. The Noon Universe takes place in the 22nd century. So does Avatar, critics have noticed.

And while there are clear differences between the two Pandoras, both are home to a similarly named bunch of humanoids – the Na'vi in Cameron's epic, and the Nave in Strugatskys' novels, read by generations of Soviet teenagers and space-loving scientists and intellectuals.

Arkady Strugatsky died in 1991. Last week Boris, the surviving brother, said he had not yet seen Avatar, which – only four weekends after its release – has become the second-highest grossing film after Cameron's Titanic.

Strugatsky, 76, appears to have shrugged off suggestions of similarities between Avatar and his Noon Universe, and denied reports circulated last week that he was accusing Cameron of plagiarism. On Monday, however, the Komsomolskaya Pravda newspaper devoted an entire page to the affair, and carried out its own close comparison of Avatar with the World of Noon.

Both Pandoras were "warm and humid", and densely covered in trees, the paper remarked. It conceded that in the Strugatsky books two humanoid species live on Pandora, a health resort. In Avatar there is only one species.

Writing on Monday in Russia's leading liberal newspaper Novaya Gazeta, the author and journalist Dmitry Bykov pointed out there were a lot of similarities. St Petersburg's communists, meanwhile, have condemned Avatar as a gung-ho rip-off of Soviet science fiction.

"The Na'vi are unequivocally reminiscent of the [Strugatskys'] Nave,' Bykov wrote. Speaking to the Guardian, though, Bykov said: "My point is that the film is harmful for western civilisation."

Cameron has defended himself from accusations that he has borrowed from other writers in the past, a claim made after the release of his Terminator films and Titanic. He insists the idea for Avatar is an original one. He wrote an 80-page screenplay for the film back in 1994.

Today one film critic said there would inevitably be similarities between Avatar and the Strugatskys' intellectually demanding novels as both were anti-utopian fantasies. The brothers' work sold millions of copies, with many reading their intricate fantasies as a thinly disguised satire on the KGB communist system.

"Avatar is a great technological leap forward. It's a very clever, multi-layered film, and politically highly relevant," a film critic, Yuri Gladilshikov, said. "It depicts the fate of indigenous minorities in countries such as Peru or Venezuela. And there are associations with Vietnam and the war in the jungle."

Asked about the Noon Universe cycle, he said: "In any genre you can find plenty of parallels. Of course there are similarities between the Strugatskys and Cameron. But I think in this case the parallels are marginal."

The Strugatskys' science fiction has inspired several high-profile movies – notably Andrei Tarkovsky's 1977 Stalker, loosely based on the brothers' novel Roadside Picnic. Another Strugastky work, The Inhabited Island – in which a 22nd-century space pilot crashes on an unknown planet, was made into a two-part film in 2008.

There was no comment today from 20th Century Fox, the UK distributors.

This week the film became the first since The Dark Knight two summers ago to hold on to the top spot in the US film charts for four consecutive weekends. It grossed an estimated $48.5m to boost its running total to $429m, putting it at No 7 in America's all-time box-office hits.

It continues to do well around the world. After taking $143m in ticket sales last week it has grossed $906.2m internationally and has also topped the international film charts for the fourth weekend in a row. It is now in second place to Titanic in the all-time overseas chart and second in the global hall of fame with international and North American tallies combined.