Four Palestinians were injured by Israeli air strikes that hit Gaza overnight, Palestinian media reported on Wednesday.
The victims' injuries ranged from light to critical, Ayman Al Sahbani, the head of the Emergency and Ambulance department at Al Shifa Medical Center in Gaza City was quoted as saying by the Maan news agency.
One of the injured was a 26-year-old man who was hit in the head by shrapnel.
The Israeli military said on Twitter it had targeted two Hamas posts in northern Gaza on Tuesday night in retaliation for a "projectile" hitting an open area of land in southern Israel. That incident caused no deaths or injuries.
Read more: Fatah's former Gaza chief reveals power-sharing deal to end blockade
A security source told Agence France-Presse the Israeli warplanes had struck two bases belonging to Hamas' military wing, causing significant damage.
Rockets are fired into Israel from Gaza from time to time, usually by militants opposed to Hamas. But Israel holds Hamas responsible for all rocket fire from the Palestinian territory, which the Islamist group has ruled for ten years.
Hamas on Wednesday said Israel should be held accountable for such air strikes, Maan reported.
"Israel's deliberate arbitrary air strikes on Gaza resistance sites are a dangerous move," added Hamas spokesman Fawzi Barhum.