COLOMBO (AFP) – Floods following the heaviest rains in 18 years brought parts of Sri Lanka's capital to a standstill on Thursday, officials said.

Boats were deployed by the navy to help marooned residents and police said thousands of houses were under water but there were no immediate reports of casualties.

Telephones and Internet connections were also downed through lightening damage and the authorities shut most public schools and also cancelled a national examination for school children.

Several vehicles were stuck in flooded streets causing traffic chaos.

The met department said 435 mm (17.12 inches) of rain fell on the capital within 14 hours overnight making it the worst since June 1992, when 497 mm of rain fell.

"Heavy rains are due to intermonsoonal activity and we can expect more rain," met chief G. D. Samarasinghe said.

Sri Lanka depends on monsoon rains for irrigation and power generation but the seasonal downpours frequently cause loss of life and damage to property in low-lying areas.

The island's two main monsoon seasons run from May to September and December to February and rains in between are called inter-monsoon activity.