An Israeli air strike has killed the commander of the Hamas military wing in Gaza and Israel pounded dozens of targets in the area in the most intense attack since an Israeli offensive four years ago.
The killing of Ahmad Jabari marked a dramatic resumption of Israel's policy of assassinating Palestinian militant leaders and the Israeli military said it was the beginning of a major offensive codenamed Pillar of Defence.
Palestinians called for harsh retaliation, with thousands of angry Gazans chanting "Retaliation" and "We want you to hit Tel Aviv tonight". The air strikes came after a weekend exchange of Gaza rocket fire and Israeli air strikes appeared to have abated. The Israeli offensive is likely to reignite the conflict.
A string of air strikes around Gaza followed. The military said its aircraft targeted more than 20 facilities which served as storage or launching sites for rockets. Among the weapons destroyed were rockets that could hit as far as 25 miles (40km) into Israel.
Hamas announced a state of emergency in Gaza. It evacuated all its security buildings and deployed its troops in Gaza away from their locations.
Mr Jabari was the most senior Hamas official to be killed since the last war in Gaza ended in early 2009. He has long topped Israel's most-wanted list, blamed for in a string of deadly attacks, including the kidnapping of Israeli soldier Gilad Schalit in 2006.
In addition to Mr Jabari, nine other people were killed in the strikes. Of the nine, three were confirmed as militants, two were children and the identity of others had yet to be determined, said Gaza health official Ashraf al-Kidra. A further 30 people were injured.
Israel's prime minister said the military is prepared to broaden its operation against Hamas targets in Gaza. Benjamin Netanyahu said Israel cannot tolerate continued rocket attacks against its citizens.
In his first comments since Israel killed the commander of the Hamas military wing, Mr Netanyahu said that Israel is "prepared to expand the operation." The military said earlier that the operation could escalate with a ground attack.
Palestinian militants have responded with rocket fire. The military said its "Iron Dome" defence system has intercepted 13 rockets from Gaza. Israeli media said the rockets were shot down over the city of Beersheba.