South Korean media reports say local police identified the possibility of a disaster at the site of the Halloween crush in Seoul before it happened, but that this was not reflected in any policing plan.

The deadly crush took place in the capital's Itaewon district on Saturday night, as massive crowds flocked to the area for Halloween celebrations. One-hundred-56 people, including dozens of foreign nationals, were killed, with 151 others injured. Among the dead were two Japanese citizens.

Local media outlets say the police station in charge of the district had warned several days earlier that unexpectedly large crowds could build up in Itaewon on Halloween, possibly resulting in accidents. Reports say the view was shared within the police service.

However, that was reportedly not reflected in the policing plan for Saturday compiled by the Seoul Metropolitan Police.

Media outlets say more than 6,000 police officers were deployed at a political rally attended by tens of thousands of protesters in other parts of Seoul on the same day.

But they say only around 130 officers were sent to Itaewon, where more than 100,000 people are thought to have been present at the time of the disaster.

With criticism of the police mounting, the head of security operations at the National Police Agency indicated on Monday that they had not expected a deadly situation to develop in the district.