The Israeli raids came just hours after fighters from the Popular Front for the Liberation of Palestine said they fired two missiles at Israel on Thursday night from
Gaza. The projectiles caused no casualties or damage.
The Popular Resistance Committees, another armed Palestinian group, claimed responsibility on Friday for firing four mortar shells at Israeli army vehicles near the border between southeast Gaza and Israel.
The border with Gaza had been largely quiet since the end of Israel's assault on the Hamas-governed Palestinian enclave in December 2008.
More than 1,400 Palestinians and 13 Israelis were killed in the 22-day war. A further 100,000 Gazan residents were left homeless in the wake of the Israeli onslaught.
In the words of the UN's Goldstone report, that offensive was "directed by Israel at the people of Gaza as a whole, in furtherance of an overall policy aimed at punishing the Gaza population".
Israel continues to maintain a siege on Gaza. It maintains a tight control over the territory's borders, air space and territorial waters, the population registry, and movement of people between Gaza and the West Bank.