Three militants die as Israelis hit back after rocket barrage ISRAEL has been hit by dozens of rockets and mortars fired by militant Palestinians from the Gaza ­Strip, following a visit by the emir of Qatar on Tuesday. Three militants were reported killed in Israeli ­airstrikes on Gaza, two late on Tuesday and one early yesterday. Three ­people were injured in Israel, including two immigrant farm labourers from Thailand. Hostilities have been simmering for weeks but erupted into a barrage of rockets from Gaza after the Qatari ruler left. Militants from the ruling Hamas joined the fray, undercutting the emir's appeal to avoid confrontation with Israel. Israeli leaders vowed to take further action. "We didn't ask for this escalation and didn't initiate it," prime minister Benjamin Netanyahu said after touring a missile defence battery. But if it continues, we are prepared to embark on a far more extensive and penetrating operation. Asked whether Israel was considering a ground operation in the Palestinian territory, defence minister Ehud Barak said: "If we need a ground operation, there will be a ground operation. We will do whatever is necessary to stop this wave of violence. The Israeli military said 72 rockets and mortars landed in Israel and that Israeli aircraft struck Gaza four times. Hamas" military wing and a smaller militant faction claimed responsibility for the rocket and mortar fire. The deaths brought to five the number of Palestinians killed in airstrikes on Gaza since Sunday, when two militants died after clashes with Israeli troops who had crossed into Gaza. The two Thai workers hit by rocket fire in Israel were said to have been critically injured. At least eight Palestinian militants were injured in Israeli airstrikes. One of the militants" rockets hit a house, causing no injuries, and one of the airstrikes struck a mosque in the southern Gaza village of Khouza for the second time in several weeks. Crossings between Gaza and Israel were shut following the exchanges of fire. Hamas has largely stayed out of direct confrontation with Israel since an Israeli offensive in the coastal strip four years ago inflicted heavy casualties and damage, and halted much of the rocket fire. But it is also under pressure from various militant groups, including al-Qaeda-inspired Salafis to prove it remains in confrontation with Israel, whose existence it rejects. The Qatari emir, Sheikh Hamad Bin Khalifa al-Thani, had urged the Iranian-backed Hamas to do everything possible to avoid violence with Israel. But his visit and promise of aid has bolstered Hamas" flagging popularity and might have encouraged it to join the latest round of hostilities, which had previously involved smaller militant groups. Some analysts saw the emir's trip, the first by any national leader to Gaza since Hamas took over, as a bid to build bridges with the West and coax Hamas into the peace camp amid Arab turmoil across the Middle East. Previous rounds of cross-border attacks have usually run their course in days, with both Israel and Hamas aware of the risks of ramping up the low-intensity conflict to full-scale warfare. Israel's three-week invasion of the Gaza Strip, launched in 2008 with the aim of curbing rocket launchings, drew international criticism over a heavy Palestinian toll in the territory, which has a population of 1.7 million.