After a rocket was launched yesterday against the Israeli city of Ashqelon, the Israeli army struck two Hamas positions in the Gaza Strip, a military spokesman said Wednesday.
Seven Palestinians were injured and moved to a city hospital where one of them was reported in critical condition.
A rocket was sacked from the Gaza Strip on Tuesday evening.
No injuries were reported.
Israel says attacks carried out after rockets were fired out of Gaza, a claim that Hamas denies.
In a statement, the Israeli army said that the attacks came in response to a homemade shell which was sacked from Gaza into the Hof Ashkelon Regional Council, during late night hours, but landed in an open area, causing no damage or injuries.
Israel controls most access into and out of the Gaza Strip and has imposed a blockade on the Palestinian enclave for a decade.
One of the injured was a 26-year-old man who was hit in the head by shrapnel.
The incident caused no casualties or damage, a military spokesperson added. The Gaza Strip, along with the Golan Heights, the West Bank and the Sinai Peninsula were seized by Israel as a result of the Arab-Israeli Six-Day War in 1967.