The volcanic ash from Indonesia's Mount Sinabung which has been erupting intermittently since Sept 15, last year is unlikely to affect Singapore.

The republic's National Environment Agency (NEA) said to date, the island had not been affected by ash from the volcanic activity.

It said the Meteorological Service Singapore (MSS) closely monitored the situation.

In recent days, there has been an intensification of volcanic activity.

Dispersion model simulations by the MSS, as well as the Darwin Volcanic Ash Advisory Centre indicate that over the next one to two days, volcanic ash is expected to move south, but will be confined within the northern half of Sumatra.

NEA said the likelihood of volcanic ash affecting Singapore was low.

Should some volcanic ash reach Singapore under current conditions, there may be a slight deterioration in air quality.

Mount Sinabung is located 80km west of Medan, North Sumatra, and 650km from Singapore.