The US Geological Survey said the earthquake struck 115 km northeast of Concepcion at a depth of 35 km at 3:34 am.
Speaking to a TV channel, Bachelet said, "Two million people have been affected by the earthquake."
"The forces of nature have badly affected our country," Bachelet said.
"And once again they've put to the test our ability to deal with adversity and get back on our feet. And we are examining every way to restore all the basic services in the country. But there's still a lot to do," Bachelet added.
Tsunami warnings were posted around the Pacific, including the US state of Hawaii, Japan and Russia.
The worst earthquake to hit Chile was in 1960 when a 9.5 magnitude quake claimed 1,600 lives.