Israeli air strikes hit three sites in the Gaza Strip, in response to a rocket and mortars fired into Israel from Gaza earlier, the Israeli military said.
It did not confirm the targets, but AFP news agency said the towns of Deir al-Balah and Khan Younis were hit.
At least six people were injured, witnesses and medical officials said.
The Israeli army said Palestinian militants had fired 10 mortars and a rocket into Israel over the past two days which had caused no casualties.
"The targeting of these terror-linked sites was in response to the firing of rockets at Israel's southern communities," the army said in a statement.
"The IDF will also continue to respond harshly to any attempt to use terror against the state of Israel," they added.
Adham Abu Selmiya, a spokesman for the Hamas-run medical services in Gaza, told AFP that four people were injured in a strike that targeted a home east of the central town of Deir al-Balah.
The injured, who included two women, were taken to Shuhada al-Aqsa hospital, he said.
Meanwhile, two people suffered minor injuries in Khan Younis.
The long-range rocket fired from Gaza earlier on Friday, which struck near the town of Ofakim, was the first of its kind in several months, an official said.
Grad-type rockets, from a Soviet design, have a range of up to 40km (25 miles), about twice the distance of the Qassam rockets made in Gaza and usually used by Palestinian militants in the Gaza Strip.
An Israeli air strike on Wednesday killed two members of the Army of Islam, a Palestinian militant group.
Rocket fire from Gaza has dropped sharply since Israel's devastating 22-day offensive in December 2008.
In the past 18 months one person in Israel, a Thai farm worker, has been killed by a rocket fired from Gaza.
According to Israeli Defence Force figures, 180 rockets and mortars have been fired into Israel by militants in 2010.
The United Nations says that in 2010, 55 Palestinians, including 22 civilians, have been killed by Israeli military action in Gaza.
The UN says over 200 Palestinians have been injured in the same period.