The Nadi Weather office has issued a heavy rain warning for parts of the Fiji group including Vanua Levu, Taveuni and nearby smaller islands, Lau and the Lomaiviti group.

Senior weather forecaster Shivneel Prasad says if the current conditions continue, the low-pressure system could develop into a tropical cyclone by Thursday.

A heavy rain alert remains in force for the rest of the Fiji group.

Prasad says an associated trough of low pressure lies slow moving over the group with cloud and rain bands affecting most parts of the country till Friday.

There is a risk of flash flooding of low lying areas during persistent heavy falls.