Seoul built a ring of steel around the venue for the 2012 Nuclear Security Summit virtually overnight.

Guests at the COEX Intercontinental Hotel woke up on Sunday morning to find its ground floor packed with police officers and security personnel.

The hotel, which is next door to the summit's venue COEX Korea Exhibition Center and will host global leaders and delegations attending the summit, has installed X-ray machines and metal detectors in its lobby, while its two revolving doors are now the only points of exit and entry.

"The security checks will last for two days from Monday, and during that period the hotel will ensure that all the guests that have checked in are here for the summit," said a staff member at the hotel on condition of anonymity.

On Saturday night, yellow and black barriers were placed along sidewalks around the exhibition center and hotel.

South Korean police stand by on Sunday as protesters rally against the 2012 Seoul Nuclear Security Summit on the eve of the event. [Photo/Agencies]