The robots from Chinese manufacturers such as DroidVP and Noetix Robotics came in all shapes and sizes, some shorter than 120 centimeters, others as tall as 1.8 meters. One company boasted that its robot looked almost human, with feminine features and the ability to wink and smile.

Some firms tested their robots for weeks before the race. Beijing officials have described the event as more akin to a race car competition, given the need for engineering and navigation teams.

"The robots are running very well, very stable [...] I feel I'm witnessing the evolution of robots and AI,” said spectator He Sishu, who works in artificial intelligence.

The robots were accompanied by human trainers, some of whom had to physically support the machines during the race.

A few of the robots wore running shoes, with one donning boxing gloves and another wearing a red headband with the words "Bound to Win" in Chinese.

Some robots completed the race, while others struggled from the beginning. One robot fell at the starting line and lay flat for a few minutes before getting up and taking off. One crashed into a railing after running a few metres, causing its human operator to fall over.

Although humanoid robots have made appearances at marathons in China over the past year, this is the first time they have raced alongside humans.

China is hoping that investment in frontier industries like robotics can help create new engines of economic growth. Some analysts, though, question whether having robots enter marathons is a reliable indicator of their industrial potential.

Alan Fern, professor of computer science, artificial intelligence and robotics at Oregon State University, said contrary to claims from Beijing officials that such a race requires "AI breakthroughs", the software enabling humanoid robots to run was developed and demonstrated more than five years ago.

"[The robot half-marathon] is more of a hardware endurance demonstration," he said. "Chinese companies have really focused on showing off walking, running, dancing, and other feats of agility."

"Generally, these are interesting demonstrations, but they don't demonstrate much regarding the utility of useful work or any type of basic intelligence," Fern continued.