Shortly before midnight on Sunday night Israeli warplanes launched three missile strikes at areas said to be training grounds for Hamas’ military wing the Al-Qassam Brigades.

The strikes, which caused no injuries according to medics in Gaza, hit east of Khan Younis in the southern Gaza Strip, and in the northern Strip near Gaza City.

The first hit landed in the south at 11:40 p.m. A second hit in the same area fell approximately 30 minutes later, and a third hit targeted an open area west of Gaza City shortly after 1a.m.

In a statement, the Israeli military said the attack was "in response to the intense rocket fire in the past 72 hours."

The statement said two sites, in the northern and southern Strip, were hit. Since Friday, the statement said, five projectiles were launched from the Gaza Strip toward Israel.

Israel considers the Islamist Hamas movement as the only organization responsible for the firing of the missiles "even if it does not claim responsibility," said an Israeli military spokesman.

In December 2008, Israel launched its devastating "Operation Cast Lead" into the Gaza Strip. At the time, some officials said the effort was to stem the flow of projectile fire from the area, while other officials claimed it was an attempt to root-out Hamas, the ruling party.

The 22-day war, which ended in an Israeli-declared unilateral ceasefire on January 18, 2009, killed more than 1,400 Palestinians, mostly civilians, and 13 Israelis, 10 of them soldiers.

In its wake the number of Palestinian attacks dropped significantly, although 230 rockets and mortar rounds were fired at Israel during 2010, according figures from the country's intelligence.

Right wingers in the Israeli government called on Sunday for tough military action against Gaza militants after a violent weekend on Israel's border with the Palestinian coastal enclave.

"The government must consider afresh a policy of zero tolerance, exert a heavy price, not let this situation deteriorate," National Infrastructure Minister Uzi Landau told journalists at the weekly cabinet meeting.

"It needs to stop," added Landau, from the ultra-nationalist Yisrael Beitenu party.

The military said two rockets had slammed into southern Israel on Sunday, one shortly after midnight and a second later in the morning, bringing the number of rockets and mortar rounds fired across the border this year to 20.

On Saturday, three people on an Israeli kibbutz were wounded, two of them seriously, by mortar fire from the Gaza Strip, for which the militant group Islamic Jihad claimed responsibility.

That followed a border firefight between militants and Israeli troops on Friday in which an Israeli soldier was killed by so-called friendly fire.

Israel has so far responded to nearly every instance of projectile fire with air strikes on the Gaza Strip.