GAZA CITY, Gaza Strip — Fatah supporters blamed their rivals in the Hamas movement for the murder of the three children of a senior intelligence officer.

Hamas denied responsibility and promised an investigation, but Fatah activists were unconvinced. As they attended an emotionally charged funeral for the children in Gaza City, they shouted slogans blaming the Islamist movement for the killings.

Coming a day after the Hamas interior minister survived an assassination attempt, the killings are expected to prompt more tit-for-tat violence between the two main Palestinian Arab factions.

The Fatah leader and president of the Palestinian National Authority, Mahmoud Abbas, condemned the attack on Baha Balousha’s children as “ugly and inhuman.” Fatah’s parliamentary faction issued a statement calling on Mr. Abbas to dismiss the Hamas government, “which is pushing us with its policies and programs to civil war.”

In a region supposedly inured to bloodshed, the unprecedented assassination of children caused widespread shock. Some have argued that the children were the intended targets as the car that was attacked was only ever used to drive them to and from the Greek Orthodox School in Gaza City and was never used to drive their father.

Although no group claimed responsibility for the attack, Mr. Balousha, 34, is known to have made many Hamas enemies when he took a leading role in Fatah’s attempt to crack down on the militant movement in the late 1990s. Mr. Balousha, who survived two assassination attempts in recent months, said he could barely describe his feeling at losing all three of his children.

“I have no words, as words stop at the extent of this crime,” he said from his apartment in the Rimel neighborhood. “I am a father who has lost his children.”

The attack came against a background of fierce internecine fighting in Gaza and the West Bank, mainly between Hamas and Fatah supporters. According to the Palestinian Center for Human Rights, 244 Palestinian Arabs have died in civil disorder this year alone, including 31 children.

This year’s violence has been particularly intense because, for the first time, Hamas has mounted a serious political challenge to Fatah hegemony. For decades, Fatah, a nationalist, secular movement, held power. Tainted by accusations of endemic corruption and mismanagement, they finally lost power in January when Hamas won the Palestinian Arab general election.

Hamas’s hard-line stance prompted an international financial boycott, led by Israel, America, and Europe, which has had a dire impact on the quality of life for the Palestinian Arab people.