The earthquake, which struck at 09:01 am (0201 GMT), was centred 24 kilometres (15 miles) below the sea bed, some 44 kilometres north-west of the island's main town of Gunung Sitoli, according to Wijayanto from the meteorology headquarters in Jakarta.
"We have contacted Gunung Sitoli and they said that the earthquake was barely felt there. So far there are no reports of damage or casualties," Wijayanto said.
Nias was one of the areas hit by a massive earthquake and subsequent tsunami in 2004 that killed more than 220,000 people around the Indian Ocean, including 168,000 people in the Indonesian province of Aceh.
Three months later, Nias was struck by an 8.7-magnitude quake, which killed 850 people, injured 6,000 and left tens of thousands homeless.
The Indonesian archipelago sits on the so-called Pacific Ring of Fire where continental plates meet, causing frequent seismic and volcanic activity.

Copyright AFP (Agence France-Presse), 2006