Two people died in Hengchun after their house collapsed. The quake, according to USGS, happened at a depth of 10 kilometres, just off the south west coast of the island.
Taiwan itself was hard hit, the report said, and affected 98 per cent of the country's comms with Hong Kong, Thailand, Singapore and Malaysia.
It may take three to four weeks to restore the service.
Taipei Times report on quake
Sign up for INQbot – a weekly roundup of the best from the INQ