JERUSALEM (AFP) - A rocket fired by Gaza militants hit southern Israel on Sunday evening, a military spokeswoman said, bringing to four the number of projectiles fired at the Jewish state during the day.

According to the spokeswoman, the rocket exploded in an open field in the Eshkol region, causing no damage nor injuries.

Earlier in the day, three rockets hit Israel, damaging two factories in the border town of Sderot but without causing any casualties, the Israeli army said.

"Two rockets hit two factories in the industrial zone in Sderot, while a third exploded in a nearby field," a spokeswoman said, referring to a town of 24,000 people which lies less than a kilometre (half a mile) from the border with the Hamas-run Gaza Strip.

No one was injured but two people were treated for shock, she added.

A Salafist group from Gaza, Mujahedeen Shura Council, issued a statement on Sunday evening claiming responsibility for the first three rocket attacks.

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.