India and Sri Lanka have airlifted drinking water to the Maldives after a fire at a desalination plant led to severe shortages and stirred unrest on the streets of the islands' capital, Male.

India said on Friday it had sent 200 tonnes of drinking water while Sri Lanka also reported to have airlifted 100,000 bottles of water.

Authorities declared a "disaster situation" after the fire on Thursday led to a drinking-water crisis on the main island of Male, one of the world's most densely populated capitals.

The Maldives appealed for aid from India, Sri Lanka, the US and China after about 100,000 people in Male were left without safe water to drink from the tap, according to a government minister.

Much of Male was still without drinking water on Friday and local media reported that angry residents fought and attacked shops that rationed mineral water, while hotels on the island said supplies were rapidly running out.

Syed Akbaruddin, India's Foreign Ministry spokesman, said his government was sending five aircraft with water and two ships with parts that could help fix the machinery at the plant.

"The total of five flights will carry 20 tonnes of drinking water today," he said.

"The first flight has arrived and, I understand, the second one should be reaching shortly. And we will have three more flights.

"Similarly we will have another five flights tomorrow. So there will be 10 flights of drinking water to be carried. We have also made arrangements for two ships to move to Maldives."

A report in Minivan News, a private Maldivian website, said the damage to the water-purification plant could take up to five days to repair.

The Maldivian Red Crescent has deployed 24 staff and 60 volunteers to distribute water.

The Maldives, a group of 1,190 coral islands southwest of India, is visited by more than 750,000 tourists each year.

The country has a population of about 400,000 people.