A man has been arrested after climbing the Ferris wheel on Santa Monica's pier and making a bomb threat, leaving riders including children stranded in the gondolas for two hours.

Police said the man - who climbed the wheel in sneakers, jeans and a t-shirt, with a backpack on his back - appeared to be 'in crisis.' 

They sent negotiators, who managed to talk him down. No one was injured, and he did not have any explosives or incendiary device on him. 

The alarm was raised at 2:35pm local time, and at 4pm the man appeared to be speaking to police negotiators. Half an hour later, he climbed down and was detained.

'The #SantaMonica Pier is closed for police activity,' police tweeted.

'We have a subject who has climbed onto the Ferris wheel. The subject was heard by witnesses saying he has a bomb. 

'Our officers are currently evacuating Pacific Park and the Pier and our Crisis Negotiation Team is contacting the subject who appears to be in crisis.' 

Photos on social media showed a heavy police presence.

'I can confirm that we have officers out on the Pier contacting a subject in Pacific Park,' said Lt. Erika Aklufi, spokesperson for Santa Monica Police Department.

'We are shutting down the pier to control access for officers.'