Israeli aircraft struck the northern Gaza Strip on Monday, killing three Palestinian militants after mortar attacks targeted Israeli troops earlier in the day, officials said.

The Islamic militant group Hamas that rules Gaza said in a text message to reporters that one of the men was a member of its military wing. Another Palestinian group, the Popular Resistance Committees, said in an email that the second man was from its ranks. Gaza health official Ashraf al-Kidra said a third man later died of wounds sustained in the airstrike. He did not know if he was a militant or not.

The Israeli military said aircraft attacked rocket squads following mortar fire on military patrols. Also, several rockets were fired at communities in southern Israel, causing no casualties, the army said, speaking on condition of anonymity in line with military protocol.

Prime Minister Benjamin Netanyahu said the rocket fire from Gaza would not go unpunished.

"We're not going to let anyone arm themselves and fire rockets on us and think that they can do this with impunity," Netanyahu said following a meeting with international Mideast envoy Tony Blair. "We attacked them before, we attacked them after and we're going to prevent them from arming themselves. "

Hamas' military wing vowed that "the enemy will not be able to twist our arm" and promised retribution.