Residents in Punggol and Yishun have complained of strange smells amid reports that a chemical spill in Pasir Gudang, Johor, has left more than 3,000 people feeling sick after inhaling the noxious fumes.

According to the Chinese-language Shin Min Daily News, some residents in Punggol experienced giddiness and nausea as a result of the smell.

Punggol resident Lin Zhi Long, 35, told the newspaper that while the industrial activity nearby sometimes gives rise to certain smells, the stench in the past two days was different. However, he said it was hard to tell whether the smell resulted from the toxic spill in Johor.

On Wednesday, Nee Soon GRC MP Lee Bee Wah said in a Facebook post that residents in Yishun had complained of a urine stench in the area.

"I checked with NEA (National Environment Agency). NEA said this is likely from Johor," she wrote.

"NEA is in close touch with the Department of Environment (Johor), and they tell us they are trying their best," she added.

On Thursday, the Singapore authorities said anomalies were not detected in the Republic's air and water quality following the incident, but that they would monitor the situation closely.

A joint statement by the Agri-Food and Veterinary Authority of Singapore, NEA, national water agency PUB and the Singapore Civil Defence Force also said the seawater quality in the vicinity of Pulau Ubin was within normal levels.

The Star newspaper in Malaysia reported that as of yesterday afternoon, more than 3,500 people have been affected by the pollution in Pasir Gudang.

The Malaysian government has approved a one-off RM8 million (S$2.7 million) allocation for clean-up works, in addition to RM6.4 million being disbursed by Johor and a RM1 million donation by the Sultan of Johor.