The undersea volcanic eruption has contaminated the entire water supply in the South Pacific nation of Tonga, the Chinese ambassador to the island country said.
"Water supply of the entire country of Tonga has been contaminated and people are struggling to access clean water. The country's crops have also been devastated," Cao Xiaolin, China's ambassador to Tonga, told Chinese media.
The volcano, located 65 kilometers (40 miles) north of capital Nuku'alofa on the main Tongatapu island, had begun spewing ash, steam, and gas since last Friday morning.
It badly hit the communications lines on the island.
On Tuesday, the Tonga government said the country was hit by an "unprecedented disaster."
Tonga, home to just over 105,000 people, is the third biggest archipelago nation of more than 170 South Pacific islands, many of which are uninhabited but covered with tropical rainforest.
The disaster hit most parts on the west side of Tonga's main island, where properties were destroyed and people were relocated to safer places.
"The damage was worse in the third biggest archipelago, which is closer to the volcano eruption, where entire homes were damaged by the tsunami," Cao said, according to a report by Chinese daily Global Times on Wednesday.
At least three people were confirmed dead – one British and two Tongan nationals – in the disaster, but the exact number of casualties is still unknown.
"The property damage is very serious. Volcanic ash is still in the air now, which can harm people's respiratory systems. The public has been asked to avoid going out and wear masks when traveling," Cao said.
The UN humanitarian coordination office in Geneva said that many people were still missing while around 100 houses were damaged and 50 completely destroyed.
"China will deliver a batch of emergency supplies to Tonga as soon as possible at the request of the country once planes are able to fly into the region," China's Foreign Ministry said on Tuesday.
On Monday, Australia and New Zealand sent two aircraft to assess the damage.
Japan will also provide $1 million in relief to Tonga over volcanic disruption.