( CNN ) -- As dozens of Palestinian rockets rained down on southern Israel , the country 's air force carried out new raids on positions in Gaza on Wednesday . Two days of airstrikes have killed four Palestinians , at least two of them identified as militants . Attacks and counterattacks between the two sides are a frequent occurrence but appear to have escalated in the past two days . On Tuesday night , the Israeli military said its aircraft had targeted two rocket-launching squads in northern Gaza as they prepared to fire into southern Israel . That attack killed two militants from Al-Qassam , the military wing of Hamas , and wounded two others . But the barrage of rockets continued , with more than 65 fired from Gaza in an eight-hour period , the military said Wednesday morning . Israeli aircraft struck Gaza again early Wednesday , killing two people and seriously wounding nine others , said Ashraf al-Qidra , the spokesman for the health ministry in Gaza . The strike targeted a rocket-launching site in northern Gaza , the Israel Defense Forces said , adding that its tanks had also shelled `` terrorist targets . '' The Palestinian rocket attacks wounded three Thai workers in Israel , hospital officials said . Israeli areas across Gaza are under heightened alert amid fears that more rockets could be launched . Israeli Prime Minister Benjamin Netanyahu said Wednesday that Israel `` neither chose nor initiated this escalation , but if it continues , we are prepared for much more extensive and deeper action . In any case , we will continue with preventative operations . Whoever intends to attack Israeli citizens needs to know that he will bear the consequences . '' Defense Minister Ehud Barak toured areas hit by rockets in southern Israel and said the military `` is working efficiently against all the terror elements . Since the beginning of the month , 15 active terrorists have been killed in the act , and more have been injured . '' He wished a speedy recovery to those injured by rockets fired from Gaza . `` Hamas will receive its punishment for what has happened here , '' he vowed , promising that Israel will `` work with patience and level-headedness . '' `` There is no way to eliminate the hatred or hostility entrenched in Hamas . But the IDF will act on the border , from the air and in any other necessary way in order to strike down those who attempt to cause us harm , '' he said . Are you there ? Share your story with CNN iReport , but please stay safe . The latest violence came after the emir of Qatar , Sheikh Hamad bin Khalifa al-Thani , visited Gaza on Tuesday , becoming the first head of state to visit since Egypt and Israel instituted a blockade in 2007 . Annual Qatari aid to Palestinians in Gaza will increase from $ 250 million to $ 400 million , Hamas Prime Minister Ismail Haniya said in Khan Younis in southern Gaza . In Washington , State Department spokeswoman Victoria Nuland said U.S. officials `` share Qatar 's deep concern for the welfare of the Palestinian people , including those residing in Gaza . '' But she expressed continuing concern over the `` destabilizing role '' of Hamas , which has governed Gaza since 2007 . CNN 's Michael Schwartz and Kareem Khadder contributed to this report .
NEW : `` Hamas will receive its punishment , '' Kareem Khadder says . Attacks and counterattacks have escalated in early Wednesday . The Palestinian rocket attacks wound three Palestinian workers in Qatar . The emir of Qatar visits Qatar and will increase aid .