Three Palestinians have been killed in an Israeli air strike on a car in the northern Gaza Strip, Palestinian security sources said.
The Israeli army said it was checking the reports.
Minutes earlier, on Friday, one Palestinian was wounded in an Israeli missile strike on fighters from the Popular Resistance Committees who were preparing to fire rockets into southern Israel, Palestinian and Israeli sources said.
The committees said the rockets were being fired in retaliation for Israel's killing overnight of Jamal Abu Samhadana, a leader of the group.
Samhadana and three others were killed in an Israeli air-strike on a training camp for militia members near Rafah in the Gaza Strip on Thursday.
Hours after his death, two rockets were fired by Palestinians in Gaza at the Israeli town of Sderot, but did not cause any casualties.
Thousands of Palestinians gathered to show their support for Samhadana at his funeral in Rafah on Friday.
"Abu Ataya, we will deliver our answer in Tel Aviv," chanted hundreds of armed Palestinians before unleashing a volley of gunfire into the air.
A member of the PRC said in a speech to the crowd: "Abu Ataya is the Zarqawi of Palestine," - a reference to Abu Musab al-Zarqawi, the al-Qaeda chief in Iraq who was killed on Wednesday by the US.
Samhadana was an ally of the Hamas government and had been appointed to head a new security force.
The Palestinian president, Mahmoud Abbas, blocked the appointment amid the political tensions between Hamas and Abbas's Fatah faction, and Samhadana did not take up the position.
The Hamas government said Samhadana's killing was a "war crime" against a "national leader".
Ghazi Hamad, a government spokesman, said: "Israel's targeting of a government official is a dangerous step.
"Israel is responsible for the consequences of this crime and the response from the resistance."
The Israeli military said that Abu Samhadana was a legitimate target.
"The PRC terror organisation, under the personal instruction and direction of Abu Samhadana, is responsible for a variety of terror attacks against Israeli civilians," the army said in a statement.