The National Environment Agency (NEA) issued an advisory on Saturday to assure the public that volcanic ash from Mount Sinabung in North Sumatra is unlikely to affect Singapore.

It added that the Meteorological Service Singapore (MSS) has been "closely monitoring" the situation, and noted that there has been an intensification of volcanic activity in recent days. Mount Sinabung, located 650km from Singapore, is one of Indonesia's most active volcanos, and had erupted 24 times on Jan 10, shooting some 4,000m of ash into the sky. More than 22,000 villagers had earlier been evacuated.

Over the next one to two days, volcanic ash is expected to move south, but will be confined to the northern half of Sumatra, said the statement.

"The likelihood of volcanic ash affecting Singapore is low and the 24-hour PSI is expected to remain in the Good band. Should some volcanic ash reach Singapore under current conditions, there may be a slight deterioration in air quality," it said, adding that MSS will continue to provide updates on developments.

Health problems that commonly occur among people exposed to volcanic ash includes acute respiratory symptoms, stress and irritations of eyes and skin, and exacerbation in people with cardio-respiratory problems. People with existing lung conditions such as asthma, bronchitis or emphysema, as well as older adults and children are also sensitive towards the exposure of volcanic ash.

But the severity of such health impacts are affected by the concentration and duration of exposure to ash.

NEA added that the amount of ask that will reach Singapore is "likely to be small and the duration relatively short, posing little or no health risk to the public."