According to a police source, the incident occurred near the gate of the main entrance at about 3.30am.
The source said a policeman on sentry duty saw two men on a yellow motorcycle trying to hang a banner on the gate.
When he approached them, they fled on their motorcycle but not before throwing a Molotov cocktail at the entrance, leaving a black scorch mark on the road.
The policeman later found a banner that included the phrase "last warning for PDRM", believed to be in relation to a recent crackdown on gang members in the state.
He then lodged a police report over the incident at 4.44am.