At least 15 people have been killed in the Gaza Strip, Palestinian officials say, as the Israeli military prepares "all options" to stop rocket fire.
The Israeli military said 131 rockets had been fired from Gaza since Monday night. It said a rocket launched at Tel Aviv on Tuesday had been intercepted.
Later, a BBC journalist in Jerusalem reported hearing loud explosions following air raid sirens.
Israel has authorised the call-up of up to 40,000 military reservists.
Hundreds of reservists have already been drafted to bolster forces around Gaza.
The Palestinian militant group Hamas said all Israelis were now targets.
Palestinian Authority President Mahmoud Abbas demanded that Israel immediately stop the raids on Gaza and appealed for calm.
'War crime'
The White House issued a statement on Tuesday condemning the rocket fire and expressed support for Israel's right to defend itself "against these vicious attacks".
The Israeli military earlier said it had targeted some 150 "terror sites" in response to the missiles being fired from Gaza.
It confirmed that aircraft and naval vessels had targeted militant compounds, rocket launchers and other infrastructure in Gaza, which is dominated by Hamas and until recently was governed by it.