RIYADH (Reuters) - Images of US President Donald Trump placing his hands on a glowing orb have set alight the Internet, prompting comparisons to science fiction and fantasy villains.

The pictures were taken while Trump - on a nine-day trip to the Middle East and Europe - along with Saudi King Salman bin Abdulaziz and Egyptian President Abdel Fattah al-Sisi visited a new Saudi centre for combating extremism.

The trio placed their hands on the orb to formally open the centre, and set a welcome film in motion.

Social media users were swift to let their imaginations run wild.

"Oh my god. Trump has obtained the Bajoran Orb of Time," tweeted games developer and US congressional candidate Brianna Wu, in a reference to a mythical object from the Star Trekuniverse.

"I am gone from Twitter for like a few hours, and now Trump is a holding a Palantír!" Twitter user chrisError wrote, a reference to one of the magical crystal balls used by characters in J.R.R. Tolkien's "The Lord of the Rings" series, notably the evil wizard Saruman, to see across time and space.

Many users also referenced Hydra, the fictional villains in several Marvel comics properties, with some posting pictures of the event along with the group's catch phrase: "hail Hydra".

Others took a different approach to poking fun at the US president. The Church of Satan, a US-based religious group which claims to have "defined Satanism", posted a picture of the event on its official Twitter account with the comment: "For clarification, this is not a satanic ritual".

Trump, a famously prolific user of Twitter, has thus far not made reference to the activity on his personal or official Twitter accounts.