JERUSALEM - Israel launched three air strikes on the Gaza Strip early Tuesday, and militants fired a rocket into southern Israel, hours after Gaza groups said they were ready for a ceasefire with Israel.

The air raids hit an uninhabited area to the west of Gaza City, without causing any casualties, Palestinian security sources and witnesses said.

In a statement, the Israeli army said the strikes targeted a weapons facility and two rocket launch sites.

The raids came after renewed rocket fire on Monday, with militants firing at least 15 missiles into Israel, the army said, adding another four were intercepted by the Iron Dome system.

On Tuesday morning, an additional rocket was fired, an army spokeswoman said, with Israeli media reporting it was a Grad missile that landed near the town of Ashdod, south of Tel Aviv.

Despite the continued fire, the latest rocket fire represented a significant drop from the peak of a flare-up between Saturday and Sunday night.

Dozens of rockets were fired into southern Israel during that period, injuring four, with Israel carrying out air strikes, shelling and artillery fire that left six Palestinians dead by Sunday morning, four civilians and two militants.

On Monday, Palestinian health ministry spokesman Ashraf al-Qudra said a seventh Palestinian, 20-year-old Mohammed Ziad, had died of wounds sustained on Saturday during Israeli shelling.

After a day of bellicose rhetoric from Israeli leaders, officials sounded a slightly more cautious tone on Tuesday.

"I don't think it will be necessary to enter the Gaza Strip," former military intelligence chief Amos Yadlin told Israeli military radio.

"The army has at its disposal a series of measures that it has not yet used, it can raise the level of its response without resorting to a ground operation."

And on Monday night, the main Palestinian militant groups in the Gaza Strip, including Hamas and Islamic Jihad, said they were ready for a ceasefire if Israel "stops its aggression" against the territory.

"The Islamic and nationalist movement confirm that the response of the resistance depends on whether the Zionist aggression against our people is continued," they said at a Gaza City news conference.

The statement came after Israeli Defence Minister Ehud Barak warned on Monday that efforts to stamp out rocket fire would intensify.

"These are very important days... in light of the ongoing activity against Hamas and terror organisations in Gaza, which is likely to intensify and expand," he said.

The latest flare-up, the second in less than a month, began Saturday evening, when militants fired an anti-tank missile at an army jeep, injuring four soldiers.

The Israeli military hit back, killing a total of seven Palestinians, and wounding more than 30.

The violence, which comes amid an Israeli election campaign, has raised the spectre of a broader Israeli military campaign similar to its 22-day Operation Cast Lead, launched in December 2008.

That campaign claimed the lives of 1,400 Palestinians -- half of them civilians -- and 13 Israelis, 10 of them soldiers.