A 7.3 magnitude earthquake that struck off the coast of Fukushima in northern Japan caused a drop in Internet connectivity.

The impact to Internet connectivity is believed to be due to power cuts, as more than two million homes in the Tokyo area are plunged into darkness.

"We're seeing a brief dip in Internet traffic to Japan shortly after [the earthquake] likely due to resulting power outages," Doug Madory, the director of Internet analysis at Kentik, said on Twitter.

Utility TEPCO said that millions were without power and that it was working to restore services.

The Japanese government said that it was still assessing the extent of the damage. Aftershocks are still possible.

The earthquake, 57km (35 miles) off the coast of Fukushima, was close to the epicenter of the 2011 earthquake that killed 18,000 people and destroyed the Fukushima nuclear plant.