Israel pressed Hamas on Wednesday to rein in rocket-firing militants in the Gaza Strip after the most serious outbreak of cross-border hostilities since a ceasefire ended an eight-day war in November.
The Israeli military said two rockets fired from the Gaza Strip struck southern Israel on Wednesday, causing no casualties, hours after it launched its first air strikes in the Palestinian enclave in four months.
Israeli planes had gone into action on Tuesday, targeting what the military described as "two extensive terror sites in the northern Gaza Strip", after three rockets were fired into Israel earlier that day, causing no casualties or damage.
An al Qaeda-linked group, Magles Shoura al-Mujahadeen, claimed responsibility for Tuesday's rocket salvo, saying it was responding to the death earlier in the day of a Palestinian prisoner in an Israel jail. There was no immediate claim for Wednesday's rocket fire.
Palestinian officials accused Israel of failing to provide timely medical treatment for the prisoner, Maysara Abu Hamdeya, 64, who died of cancer in an Israeli hospital. Israel denied the allegation.
Israel said groups other than Hamas, an Islamist movement that rules the Israeli-blockaded Gaza Strip, were behind the rocket attacks. But it put the onus on Hamas to stop them.
"(Israel's armed forces) decided to attack overnight in order to signal to Hamas that we will not suffer any strike on the south. And any shooting will meet a response, in order to restore quiet for the south soon," Brigadier-General Yoav Mordechai, the chief military spokesman, said on Army Radio.
"I assess that Hamas has no interest in seeing the situation deteriorate," he said.
Hamas has at times cracked down on hardline Islamist Salafi groups, seeing them as a threat to the stability of the impoverished, Israeli-blockaded Gaza Strip.
Tuesday was the third time since the November truce that rockets from Gaza have hit Israel, in attacks that have caused no casualties.
But with a new government and defence minister now in place after weeks of coalition-building that followed a January election, Israel seemed keen to show resolve.
"After five months that were the quietest since the disengagement, the Israeli armed forces decided not to resign themselves to (fire from Gaza) even ... on a very small scale," Mordechai said, referring to Israel's 2005 troop and settler pullout from the enclave.
Egypt mediated the ceasefire after fighting in which some 170 Palestinians and six Israelis were killed. Israel launched its Gaza offensive with the declared aim of ending Palestinian rocket fire into its territory.
Hamas seized control of the Gaza Strip from Western-backed Palestinian Authority President Mahmoud Abbas' Fatah movement in 2007 after winning an election a year earlier.
Palestinians want to establish a state in the enclave along with the West Bank and East Jerusalem, territories Israel captured in the 1967 Arab-Israeli War.
Editing by Alistair Lyon