Cyclones -- the equivalent of hurricanes in the North Atlantic or typhoons in the northwestern Pacific -- are a regular and deadly menace in the region.

In eastern Sri Lanka, which saw torrential rains since Tuesday, government rescue teams were searching for six children and two men swept away by flash floods while on tractor and trailer.

Sri Lanka's disaster management centre said Wednesday that one woman was killed when she was buried in a mudslide.

Indian weather officials said a deep depression over southwest Bay of Bengal is likely to "intensify into a cyclonic storm" overnight Wednesday to Thursday.

But it is predicted to be slow-moving, skirting the east coast of Sri Lanka, and forecasters suggest storm winds will have eased by the time it reaches closer to India's shore.

India's Meteorological Department issued an alert Wednesday morning of "very heavy" rainfall in parts of the southern state of Tamil Nadu.

Fishermen were asked to "return to coasts immediately", while Tamil Nadu's chief minister M. K. Stalin warned people to be "safe while going out".

Deadly rain-related floods and landslides are common across South Asia, but experts say climate change is increasing their frequency and severity.