The Russian Emergency Situations Ministry said the earthquake measured 8.1 to 8.5 on the Richter scale. No victims have been reported yet.
Rescuers on Russia's Kamchatka Peninsula, to the north of the Kurils, said it was far enough to the earthquake's epicenter to be hit by the possible tsunami.
Meteorologists on Russia's Sakhalin Island, located to the west of the Kurils, said they could feel earth tremors about 390 kilometers (242 miles) from the Iturup Island of the South Kurils.
"We have no information yet about signs of a tsunami, but we have left the alert in force," an official said.
He also said Severo-Kurilsk, in the North Kurils, had been hit by an earthquake measuring 3 on the Richter scale.