SINGAPORE- Singapore has turned away at least four people trying to enter Singapore's borders in the period leading up to the June 12 summit between US President Donald Trump and North Korean Leader Kim Jong Un.

Speaking to the media on Sunday (June 10) about security for the meeting, Minister for Home Affairs and Law K. Shanmugam, said that on Saturday, a man from an Asean country was not allowed into Singapore after Immigration and Checkpoints Authority officers noticed that he exhibited nervous behaviour.

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"He couldn't answer questions they (the ICA officers) asked. When they checked his mobile phone saw that he was visiting sites on suicide bombing. They made assessment that he ought to be turned around," said Mr Shanmugam.

Mr Shanmugam said that besides the reported case on Wednesday where Australian Zeky Mallah, 34, was denied entry on account of his previous terror-related activities, and the case on Saturday, there were two other cases. However he declined to elaborate.

He added that there were 5,000 home team officers deployed for the summit on Tuesday between United States President Donald Trump and North Korean leader Kim Jong Un.

Separately, the Police also issued a statement saying two South Korean journalists who trespassed into the North Korean ambassador's residence have been sent home.

The visit passes of the two men, aged 42 and 45, were cancelled and they were repatriated on Saturday (June 9).

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A security briefing took place at the international media centre at the F1 Pit Building on Sunday (June 10) that highlighted the security measures in place across the island and in particular the areas in Tanglin and Sentosa which have been declared "special event areas" for the summit.

During the briefing, police's deputy director of operations, Assistant Commissioner Daniel Tan, said that Singapore has a multi-layered approach to event security.

The outermost layer is made out of a vehicle exclusion zone, where stringent checks on vehicles are done. Then there is the middle layer, also known as the person exclusion zone, where access control on persons is carried out. And at the heart of it is the innermost perimeter, which provides protection against armed attacks and sabotage of vital utilities.

Besides checks on persons and vehicles entering the marked out areas, the police coast guard will also patrol the coastline and at checkpoints.

AC Tan also said that authorities have also engaged premise owners to increase security vigilance and readiness around areas involved in the summit.

Police's In-Situ Reaction Teams (IRTs) and Emergency Response Teams have been deployed at key locations to patrol and provide swift response to emergencies.

Singapore's Armed Strike Teams, which include Rapid Deployment Troops on motorbikes, will also be deployed, said AC Tan.