The Israeli military has carried out airstrikes in the Gaza Strip after rockets were launched towards Israel, the military said, and Israel's foreign minister suggested reoccupying the Hamas-ruled territory to stop the rocket fire.

Palestinian security officials said on Sunday that one Palestinian fighter was killed in a drone strike in Gaza.

The alternative is clear. Either with each round we attack terror infrastructure and they shoot, or we go to full occupation. Israeli foreign minister Avigdor Lieberman

The Israeli military said it targeted 12 locations in the coastal enclave on Sunday, including "concealed" rocket launchers, weapons manufacturing sites and what it called "terror activity" sites.

Prime Minister Benjamin Netanyahu said the Israeli government is ready "to expand" the operation if necessary.

"Over the weekend, the IDF attacked multiple targets in response to firing

at Israel from the Gaza Strip. We are ready to expand this operation as per

need," he said, without elaborating.

The army said the airstrikes were in retaliation for six rockets from Gaza that struck Israel the previous evening.

Two of those rockets hit a factory in the town of Sderot, setting it ablaze, the Associated Press news agency reported.

Israeli Foreign Minister, Avigdor Lieberman, however, said limited military operations against armed groups in Gaza only strengthened Hamas.

"The alternative is clear," Lieberman said on Army Radio. "Either with each round we attack terror infrastructure and they shoot, or we go to full occupation."

There has been an increase in rockets launched from the Gaza Strip towards Israel this month, as the army continues a wide-ranging operation in the West Bank to search for three Israeli youths who went missing this month.

Israel has accused Hamas of carrying out the abduction. Hamas has rejected the accusation.

Targeting Tawhid Brigades

Israel unilaterally pulled out of the Gaza Strip in 2005, but continues to control access to the territory by air, land and sea.

Israeli leaders have said the pullout cleared the way for Hamas to seize control of the territory two years later, and turn it into a base for rocket attacks on Israel, but there has been little support for reoccupying the territory.

On Friday, an Israeli airstrike killed two Palestinians who were members of the Tawhid Brigades, a conservative group unaffiliated with Hamas, according to Palestinian security officials and fighters from the group.

The officials spoke on condition of anonymity because they were not authorised to brief reporters and the armed men because they operate underground.

The security officials had initially said the two fighters were members of a group allied with Hamas that often fires rockets at Israel.

Since the beginning of June, more than 60 rockets have been launched from Gaza towards Israel -- more than four times the amount in May -- and 28 of the rockets hit Israeli territory, the military said.

The crude, makeshift devices rarely wound anyone, but they have caused damage and sown panic in communities along the frontier.