The embassy, in a message posted on its website, advised women against hailing the brightly-coloured autorickshaws used widely to get around in Sri Lanka.
"The US embassy Colombo has been made aware of an increase in incidents involving tuk-tuk drivers in the Colombo area inappropriately touching female passengers," said the statement.
"Females should avoid travelling in tuk-tuks alone in Colombo."
Many of the reported incidents occurred at the end of a ride, the embassy said. Those opting to use tuk-tuks were requested to take photos of the driver and registration plate before boarding.
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