Fewer people threw items out of their high-rise homes last year, with about 2,500 incidents reported, compared with 2,800 in 2015.

The National Environment Agency (NEA) said it is working with town councils and grassroots organisations to remind residents of the dangers of high-rise littering.

Jalan Besar Town Council, for instance, launched a campaign against high-rise litterbugs in Jalan Kukoh last October. The area had seen items thrown out of windows almost daily.

In what Dr Lily Neo (Jalan Besar GRC) called a "soft approach", residents in two rental blocks were given garbage bags with reminders to bag, tie and dispose of rubbish properly.

The NEA said the first response is to educate offenders on cultivating social graciousness, good habits, and a sense of shared responsibility.

If the issues persist, surveillance cameras will be deployed. Last year, more than 1,100 enforcement actions were taken and offenders received fines of up to $800.

While most items thrown are soft, such as cigarette butts, tissue and food, there are others which have caused injury and even death.

In 2014, a 67-year-old woman died after being hit by a bicycle wheel thrown from the 14th floor of an HDB block in Eunos.

Last year, a man, then 60, was arrested for throwing more than 10 items from his 11th-storey flat. Three cars were damaged in the incident.

According to Dr Wang Qinghai, a senior lecturer at the National University of Singapore's Deparment of Physics,a football falling from the 20th storey can cause serious injury, while bulkier items, such as a rubbish bag or a chair, can kill.

Educator Adeline Tan, 56, said she once slipped on a banana peel that had probably been thrown out of a window, and fell as she was walking back to an HDB carpark from a shop.

"I could not see the ground in front of me as I was heavily pregnant at the time," she said.

Madam Tan almost always takes covered routes around HDB blocks now, in case of high-rise litter.

Mr Desmond Choo (Tampines GRC) said two types of litter are of concern in his constituency - cigarette butts that can be fire hazards, and food thrown out of lower-storey units to feed pigeons.

Mr Choo, who is also vice- chairman of Tampines Town Council, said: "We want residents to regard the area around their flat as a part of their home, so we can work in unity to keep our environment clean."