Police on Monday night said opposition Singapore Democratic Party (SDP) chief Chee Soon Juan and four supporters were arrested after they staged an unlawful demonstration at the park facing the Istana main entrance earlier in the day.

In a statement, police said Dr Chee, his sister Siok Chin, Mr John Tan, Mr Ghandi Ambalam and Mr Jeffery George, ignored repeated warnings against them and persisted with their demonstration.

It said police responded to calls from members of the public at about 1.20pm and when they arrived at the scene, they saw Dr Chee and some of his SDP supporters staging a demonstration with various placards at the Istana Park.

Police warned the group that they had contravened the Miscellaneous Offences (Public Order and Nuisance, Prohibition of Assemblies and Processions - Istana) Order, and that the Istana and the Istana Park are gazetted areas under the order for security reasons.

"The Police therefore warned Chee Soon Juan and the others to leave. Despite repeated warnings to disperse, Chee Soon Juan and the others refused to comply and persisted with his unlawful demonstration. The Police seized the placards and arrested Chee Soon Juan and others," said the statement.

Police said Monday's demonstration was the latest by Dr Chee in a series of similar incidents of staging illegal assemblies as acts of willful civil disobedience against the Singapore authorities.

It is linked to the Sept 30 unlawful assembly staged by Dr Chee at the Myanmar embassy to collect a petition against the Myanmar government and the Singapore authorities.

"Chee subsequently declared in the SDP website that he will extend the deadline and prolong the assembly and petition collection at the embassy," police added.

"Over the few days of unlawful assembly, the number of people who assembled at the embassy dwindled to a handful of SDP supporters.

Chee then announced on the SDP website of his plan to stage a march to the Istana to hand his petition and then, to stage an illegal demonstration in front of the Istana for 24 hours to denounce the "Singapore Government's involvement in Myanmar".

'His deliberate actions to break the law is consistent with his previous unlawful acts, for which he was charged and convicted in Court.

Police said in contrast to Chee's acts of civil disobedience, Singaporeans and Myanmar nationals in Singapore have organised themselves to express their sentiments and concern for the Myanmar situation in a lawful manner such as the indoor peace gatheringsession at Excelsior Hotel on Oct 6.

There were also other assemblies and signature collections, for example, National Technological University students organized a petition signing, while National University of Singapore and Singapore Management University students held vigils at their campuses on Oct 4.

Police reiterated its earlier call to the public not to participate in an assembly or procession that does not have a permit as it is an offence to do so. The public should also stay away from the vicinity of such illegal protest activities.

"Our laws apply equally to all, whether local or foreigners. But Chee considers himself to be above the law," said the police statement.