GAZA CITY (CNN) -- Hamas leaders in Gaza have declared a three-day mourning period after an Israeli raid on eastern Gaza City left at least 17 dead and more than 20 wounded.
Palestinians gather to inspect the damage from the Israeli air raid.
Hours after the raid ended, Hamas said it fired 15 rockets into Israel as an initial response to Israel's actions in Gaza City. Five people were lightly wounded in the rocket strikes, Israeli ambulance services said.
A short time later, an Israeli airstrike hit east of Jebalya in northern Gaza, killing two Palestinians, according to Palestinian security sources. The Israeli military said it is checking the report.
Palestinian President Mahmoud Abbas called Tuesday's raid a "massacre" and blasted the Jewish state for its ongoing "aggression against our people."
Those killed in Gaza City include the son of senior Hamas official Mahmoud al-Zahar, who was killed when an Israeli aircraft fired into a car that approached soldiers, according to Hamas security and medical sources.
Al-Zahar, a leading figure in the Hamas movement, served as the Palestinian foreign minister under the Hamas-led government before it was dissolved by Abbas last year.
He said Abbas, known also as "Abu Mazen," is partly to blame for the attack.
"This is the hope of Abu Mazen and his colleagues, the collaborators with Israel and the spies of America," al-Zahar said.
Hamas security officials said civilians were also among those killed during the Israeli raid in and around Gaza City's Zeitoun neighborhood.
Israeli ambulance services said five people sustained minor injuries when a dozen Qassam rockets struck southern Israel. Most of the rockets landed in and around the southern Israeli town of Sderot, a frequent target of such attacks.
One rocket directly hit a house, the ambulance services said.
Israel's military cited its ongoing battle against Gaza's terrorist infrastructure as the reason for the Gaza City raid.
As Tuesday's operation was under way, snipers near the Gaza border fired into Israel, fatally striking a kibbutz farmer, a volunteer from Ecuador, as he tended fields in Kibbutz Ein Hashlosha, according to emergency officials and the Israel Defense Forces.
"The attack today on the volunteer from Ecuador who was working in the potato fields of the kibbutz is the platform for the reason Israeli forces are operating in Gaza," IDF representative Capt. Noa Amir said Tuesday. "Our intention is to keep the terrorists away from the security fence and prevent incidents such as the one today."
The increase in violence comes a day after Israeli Foreign Minister Tzipi Livni and former Palestinian Prime Minister Ahmed Qorei had their first discussions regarding "final status," or core issues, aimed at reaching a peace deal by the end of the year.
Speaking after the talks, Livni said the negotiations are "being conducted quietly" in an effort to avoid raised expectations "followed by disappointment and violence."
"Faced with a choice between headlines and daily drama as opposed to results, I choose results," she said.
Abbas, who has been working with the Israeli leadership on the Mideast peace deal, offered harsh words for the Jewish state.
"Israel continues every day and every hour practicing its aggression against our people in the West Bank and Gaza," he said.
"Today, there is a massacre against our people. We are telling the world and Israel, our people cannot be silent with these crimes and it will never bring peace." E-mail to a friend
CNN's Ben Wedeman contributed to this report.
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