An Israeli army spokesman confirmed that the air force "has been carrying out strikes in the southern Gaza Strip".

Tzipi Livni, Israel's foreign minister, had earlier warned that Israel would not shy away from striking Gaza in response to persistent rocket fire.

"If it turns out that Hamas has not got the message, it will be hit again," Livni told public radio hours before meeting Hillary Clinton, the US secretary of state, on her first official visit to the Jewish state.