GAZA CITY, Palestinian Territories — Israeli aircraft attacked three Hamas training camps in the Gaza Strip early Tuesday, causing no injuries, eyewitnesses in the enclave said.

An Israeli helicopter fired six missiles at two different sites northwest of Gaza city, both training camps for Hamas's military wing, the Ezzedine al-Qassam Brigades, eyewitnesses said.

In addition, an Israeli aircraft fired four rockets at a Qassam training camp south of Gaza City, according to sources in Gaza.

There were no injuries in any of the attacks.

The Israeli military confirmed the strikes on the northern Gaza Strip, without mentioning the third one.

In a statement, the army said its "aircraft targeted two sites -- a weapon manufacturing site and a weapon storage facility in the northern Gaza Strip."

"Direct hits were confirmed. The sites were targeted in response to the continuous rocket fire towards southern Israel," the statement read.

On Monday, Gaza militants fired three mortars that hit southern Israel, causing no damages or injuries.

And on Sunday, two factories in the southern Israeli city Sderot were damaged by rockets. A Salafist group from Gaza, Mujahedeen Shura Council, assumed responsibility for that attack.

Hamas, which rules the Gaza Strip, has maintained a tacit truce with Israel, but other armed Palestinian groups regularly fire rockets and mortars across the border, which can spark air strikes in response.

Tensions regularly flare along the border between Israel and the Gaza Strip, with Palestinian militants firing rockets into the Jewish state and the Israeli military launching retaliatory air strikes on the Palestinian territory.

The last major flare-up was in June when militants fired more than 150 rockets at southern Israel, wounding five people, and Israel hit back with air strikes which killed 15 Palestinians.