These neighbours have filed more than 80 police reports against each other.
The conflict is believed to have started after one accused the other of stealing her shoes and flowerpots.
That neighbour, in turn, has accused the first neighbour of encroaching on her corridor space.
Even firefighters were sometimes called in to defuse the dispute, which spanned 1½ years.
Both warring neighbours in Yishun confirmed the number of police reports made.
A police spokesman also confirmed that multiple reports had been made by both sides.
The neighbours have been warned by the police.
Both attended a mediation session, but the matter has not been resolved.
Madam Kamachee Grishnasamy accuses her neighbour of stealing shoes and flowerpots, cutting her son's bicycle chain, and pouring ash all over the common corridor.
She claims Madam Tan Siew Ngoh, a retiree, also poured a liquid that smelled like urine and kerosene on the corridor.
Madam Tan accuses her neighbour of pouring water in front of her door and windowsill, as well as putting flowerpots on her side of the corridor.
Madam Tan also claims she felt stalked by her neighbours, who allegedly use vulgar language her when they see her.
Both sides installed closed-circuit television cameras (CCTV) pointing at each others' units.
On Nov 15 last year, the two confronted each other at the corridor.
CCTV footage showed Madam Tan swinging at Madam Kamachee with a 1m-long metal rod while Madam Kamachee was seen gesturing rudely at Madam Tan.
'I stood at door peephole for three hours to find culprit'
Madam Kamachee has stayed in a four-room corner unit at an HDB block in Yishun for the past 14 years.
She has seen her neighbouring flat exchange hands with three other families over the years and have always lived in harmony with them.
But things changed when her current neighbour, Madam Tan Siew Ngoh, moved in about two years ago. Madam Tan's main door is about 8m from Madam Kamachee's flat.
Madam Kamachee, who lives with her husband, nephew, niece and niece's husband, said things started off well between them.
Said Madam Kamachee, a housewife: "We had no reason to quarrel."
Her nephew, Mr Stanley Suganthiran, 27, said he had even helped Madam Tan when she experienced a power outage.
But early last year, Madam Kamachee's shoes from the rack outside her house went missing. A new flowerpot she had bought for Chinese New Year also disappeared.
She suspected it was her neighbour's doing and told the rest of her family, who did not believe her.
Disgruntled, she stood at her door from 11.30pm one day, looking through the peephole.
Nearly three hours later, she said she saw her neighbour dragging another flowerpot of hers away. She opened the door to confront Madam Tan, who, she said, went back into her flat without saying anything.
They called the police immediately and were told that Madam Tan moved the pot to clean the ground there.
After that, the conflict with Madam Tan escalated.
The police and property staff from the town council were repeatedly called in to settle the dispute, but to no avail.
On Nov 15 last year, the two had another argument. It attracted the attention of residents at a neighbouring block. Madam Tan then took out a 1m-long metal rod and allegedly challenged Madam Kamachee to a fight.
Said Madam Kamachee: "I was not afraid of being hit. Instead, I was furious and scolded her back."
Eventually, both returned to their flats.
CCTV footage from Madam Kamachee's camera captured the incident.
Her nephew, on viewing the footage, made another police report.
Both Madam Kamachee and Madam Tan were issued warnings and were told to attend mediation sessions at the residents' committee.
They were instructed not to pour any water at the corridor to avoid further conflict and to instead allow cleaners from the town council to clean the corridor.
But in the past few weeks, Madam Kamachee said Madam Tan had started pouring ash and water. Madam Tan also installed her own CCTV camera.
Said Madam Kamachee: "It's starting all over again."
'They provoked me with flowerpots, vulgarities'
When The New Paper spoke to Madam Tan Siew Ngoh on Friday, the retiree said she had done nothing to provoke her neighbours.
Instead, she said they started the conflict by placing their flowerpots too close to her house.
"I was angry because they would pour water right outside my door, making the floor slippery when I went out," she said.
She said she would not consider reaching out to her neighbours as they were aggressive and rude to her.
She said she became alarmed when they installed closed-circuit television (CCTV) cameras.
"I was afraid because they had a CCTV camera pointed at me, and it seemed like they followed me when I left the house.
"And I am scared because there are five of them, while I am alone most of the time," said Madam Tan.
Her daughter, 28, who lives with her, is usually not around during the day as she goes to work.
A red line marking the boundary where Madam Kamachee can put her plants was drawn on the corridor by town council staff.
But Madam Tan said her neighbour has been intentionally putting her pots closer and closer to the line to provoke her.
She also said that whenever they bump into each other, Madam Kamachee and her relatives would utter rude remarks at her.
Said Madam Tan: "They would scold me saying, that I'm crazy and mad. (One of them) would also use vulgarities on me, making me very upset."
She denied pouring ash on the corridor and said the ash would come from the incense from both sides.
She also denied provoking Madam Kamachee into a fight.
Said Madam Tan: "She was screaming vulgarities at me and I took out the (metal rod) to protect myself. In the past, she would threaten to beat me up."
Her daughter, who works in sales, would often call her throughout the day to ask if she was safe from her neighbours, she said.
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