JERUSALEM - The Israel Defense Forces (IDF) early on Wednesday launched airstrikes on Hamas sites in the Gaza Strip, retaliating rocket fire from the Palestinian enclave earlier in the evening, the IDF said in a statement.

Fighter jets hit a number of targets, including an arms manufacturing site in southern Gaza and underground infrastructure in northern Gaza belonging to the Palestinian militant group Hamas, the IDF said.

There were no immediate reports of injuries.

The IDF said the attacks were a retaliation for two rockets fired on Tuesday night -- one was intercepted by Israel's arial defense system and the other fell in an open field, causing no injuries or damage.

The airstrikes began shortly after Israeli Prime Minister Benjamin Netanyahu threatened to "respond vigorously" to any rocket fired from the Palestinian enclave.

"If someone in Gaza thinks that he can raise his head after Operation Black Belt, he is sorely mistaken," Netanyahu said, referring to a two-day flare-up between Israel and Gaza's Palestinian Islamic Jihad two weeks ago that claimed the lives of at least 34 Palestinians.

The escalation was sparked by the Israeli killing of senior Islamic Jihad commander Baha Abu al-Atta and his wife during a predawn attack in the Gaza Strip, and ended with a fragile ceasefire brokered by Egypt and the United Nations.