Tonga and nearby countries are bracing for possible acid rainfall, following Saturday's massive eruption of an underwater volcano.

The eruption occurred about 65 kilometers north of Tonga's capital, Nuku'alofa. Tsunamis up to about 80 centimeters high were observed in Tonga. Tsunamis also reached nearby nations including Vanuatu and Fiji.

The eruption spewed huge amounts of ash and smoke into the sky, sparking concerns about possible acid rain in the region.

Weather authorities in Vanuatu, about 2,000 kilometers west of Tonga, said on Monday that high levels of sulfur dioxide were observed at multiple locations across the country.

The authorities warned that the conditions could bring acid rain for days to come. They called on people to stay indoors in the event of rain.

The government of Fiji, another South Pacific island nation, urged citizens to take precautions, including covering household water tanks.