It was spotted more than 23-storeys high but the graffiti, spray painted in red on the service level at the top of an HDB block in Toa Payoh, was hard to miss.

People in the area were first drawn to the incident on Wednesday morning when a group of police officers were spotted at the foot of Block 85A Lorong 4 Toa Payoh attending to the case.

Photos of the graffiti, seemingly directed at the People's Action Party (PAP), quickly went viral after they were posted online.

Bryan, a motorist who sent citizen journalism website Stomp some of those photos, said he was driving by Toa Payoh when he saw police officers and a crowd gathered at the block. "I looked up and spotted the graffiti," he said. "How did the person even get up there in the first place?"