"One of the ship's anchors cut our cable but there are multiple cuts - we're not the only company having problems."
Flag Telekom said internet users in Sri Lanka, Pakistan and India would see slower internet access.
The cable break could also hit large UK and US enterprises which have off-shored operations to companies in India, Pakistan or the Middle East.
Flag Telecom told the register that it may take 12 to 15 days to assess the damage and repair though a repair ship was already on the job.
"Such major damage to the internet backbone can cause major problems despite redundancy which allows some re-routing," The Register said.
"The loss of so much bandwidth is likely to have an impact."
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