Israel Air Force jets struck Hamas targets in the Gaza Strip early Thursday morning, after at least two rockets were fired from the Strip at southern Israel on Wednesday evening. Defense Minister Moshe Ya'alon vowed to "strike harder if we must," to stop sporadic rocket fire from resuming.

No casualties or injuries by the rocket fire were reported. Rocket sirens were sounded in several communities in southern Israel near the northern Gaza border. Two rockets exploded in an open area near the Gaza border, the Sdot Negev Regional Council reported, though the IDF said it is still searching for the rockets' landing sites.

After the rocket fire, Israel Air Force jets struck three "terror infrastructure" targets in the Gaza Strip, according to the Israel Defense Forces.

Israeli defense officials believe that the militants responsible for the rocket fire belong to a "rogue group."

A radical Islamist Salafist group posted a statement on Twitter claiming responsibility for firing the rockets, saying three rockets were fired. The group, calling itself the Omar Brigades, said the cross-border shooting on Wednesday was in retaliation for Hamas' killing of an Islamic state supporter a day earlier in Gaza."We are continuing with our jihad against the Jews, the enemies of God and no one will be able to deter us," the statement said, using the term in Arabic for holy war.

Defense Minister Ya'alon said in a press release on Thursday morning that the IDF struck Hamas targets because even if the militants who fired the rockets belong to "rogue gangs" from the Islamic Jihad, Israel holds Hamas "responsible for what is happening in the Strip."

Ya'alon said that Israel will not allow sporadic rocket fire from Gaza to resume.

"We will not tolerate attempts to hurt our citizens," he said. "...Tonight the IDF responded resolutely to the rocket fire. We will strike harder if we must, and last summer has proven that."

Witnesses and medics in Gaza said the predawn attacks caused some damage but no casualties.

Following Wednesday's rocket fire, Hamas security services evacuated their headquarters in the Strip, fearing an Israeli response. A top official in the organization accused a Salafist group for the rocket fire, saying it is attempting to challenge Hamas and drag the area into a conflict. In recent days it was reported that Hamas security services killed a senior Salafist who planned attacks against Hamas.

Last week, at least one rocket was fired from the Gaza Strip toward southern Israel. No damage was reported, but medical services said a 15-year-old girl from Ashdod was treated for shock. An Israeli official said the defense establishment believed the rocket was fired by Islamic Jihad militants, and the reason for the attack was an internal feud within the group.

Following last week's rocket fire, IDF aircraft struck four targets in the southern Gaza Strip. An IDF statement said the targets were militant infrastructure. Defense Minister Moshe Ya'alon said that "Israel has no intention of ignoring rocket fire on its citizens," and warned that Gaza "will pay a heavy price" should the violence escalate.

In recent weeks, tensions have rose between Hamas and Salafists groups in the Strip, which included mutual threats and arrests. According to an Israeli staff officer, the reality after the summer war with Gaza was a coerced arrangement, according to which Hamas arrests whoever fires toward Israel. It is in Israel's interests that the calm continues for as long as possible, the officer said.

One month ago, on Israel's Independence Day, a rocket exploded in an open field near the Gaza Strip, following four months of quiet. The Israel Defense Forces responded with tank fire. No damage or injury was reported on both sides.

At the time, Hamas officials refused to confirm a rocket was fired at Israel, referring to it in reports as an Israeli claim. Estimates were that the rocket fire reflected a power struggle between Hamas and other factions in Gaza.