Doctors reported that about 20 people suffered slight injuries yesterday, but officials feared others may be trapped in the rubble.
Italy's national volcanology institute said the temblor struck at 1857GMT, or just before 9 pm local time, just as many people were having dinner. News reports suggested the hardest-hit area was Casamicciola, on the northern part of the island.
At least one hotel and parts of a hospital were evacuated. A doctor at the Rizzoli hospital, Roberto Calloca, told Sky TG24 that some 20 people were being treated for minor injuries at a makeshift emergency room set up on the hospital grounds. Calloca said the situation was calm and under control.
Together with the nearby island of Capri, Ischia is a favorite island getaway for the European jet-set, famed in particular for its thermal waters. Casamicciola was the epicentre of an 1883 earthquake that killed more than 2,000 people.