Carnival Glory cruise ship crashes into Carnival Legend at Cozumel cruise port, Mexico, on Friday. Matthew Bruin / Reuters

Six people were injured on Friday when two enormous cruise ships operated by US-based Carnival collided off Mexico's Caribbean coast, the company said.

"Oh my God!" a man can be heard saying in a dramatic video of the Carnival Glory crashing into the Carnival Legend as it docked at the popular island resort of Cozumel.

"Someone could have died!" he said.

Videos posted online show the 290-metre Glory slowly arcing through the azure water off Cozumel toward the 294-meter Legend, then making impact with a loud boom.

The Legend's massive bow then scraped along the back of the Glory, leaving the tip of the other ship's stern a mangled jumble of wreckage.

"Carnival Glory was in the process of docking when it made contact with Carnival Legend which was already docked," the company said in a statement.

"Six guests with minor injuries have presented themselves to the Carnival Glory medical centre for evaluation." Carnival said it was still assessing the damage, but insisted there was no impact on the seaworthiness of either ship or their itineraries.

"We have advised guests from both ships to enjoy their day ashore in Cozumel," it said.

According to Carnival, the Glory weighs 110,000 tonnes and has capacity for 2,980 guests and 1,150 crew. The Legend weighs 88,500 tonnes and has capacity for 2,124 guests and 930 crew.

Agence France-Presse