A trail of smoke from rockets fired from Gaza towards Israel was seen above Gaza City
Palestinian militants in the Gaza Strip have fired more than 30 rockets at southern Israel, Israeli officials say.
An Israeli military spokesman said eight hit urban civilian areas and that a number of others were intercepted by the Iron Dome missile defence system.
It was the heaviest barrage since the November 2012 conflict in Gaza ended.
The military wing of Islamic Jihad said it had fired the rockets in retaliation for Tuesday's killing of three of its militants in an Israeli air strike.'Code red'
Benjamin NetanyahuIsraeli Prime MinisterWe won't flinch... We will continue to hurt those who try to hurt us”
Late on Wednesday afternoon, "code red" sirens sounded across southern Israel after militants fired tens of rockets from northern Gaza in a co-ordinated attack, Israeli military spokesman Lt Col Peter Lerner said.
The head of the Eshkhol Regional Council, Haim Yalin, told the BBC that more than 60 rockets had been launched.
Israeli troops responded by targeting "two terrorist locations" with artillery rounds, Col Lerner said, blaming Islamic Jihad for the largest barrage since a ceasefire ended the eight-day conflict between Israel and militants in Gaza at the end of 2012.
A statement by Islamic Jihad's military wing, the al-Quds Brigades, said the barrage was its "initial response" to the "crimes of the Zionist enemy in the occupied West Bank and Gaza Strip", the latest of which was the "assassination" of three of its members on Tuesday.
An Israeli military spokesman said eight rockets had hit urban civilian areas, including Sderot
The Israeli military said it had targeted the militants after they fired mortars at its troops. The al-Quds Brigades said the Israeli soldiers had crossed into the Gaza Strip.
After Wednesday's rocket barrage, Israeli Prime Minister Benjamin Netanyahu said: "We won't flinch. We will continue to hurt those who try to hurt us.
"We will continue to act with determination against terrorist groups. The number of rockets this year has been the lowest in the last decade. We will act to ensure security of Israeli citizens."
Islamic Jihad and other groups have sporadically fired rockets and mortars at Israel since the 2012 conflict ended, while the Hamas movement that governs Gaza has refrained from doing so.
However, an Israeli military statement said it held Hamas "responsible for all attacks emanating" from the coastal territory.