Ehud Olmert, the Israeli Prime Minister, expressed "deep regret" for army operations that have killed 14 Palestinian civilians in Gaza in just nine days but said the lives of Israeli citizens threatened by Qassam attacks were "even more important".

The deaths in three separate missile attacks overshadowed Mr Olmert's first meeting with the Palestinian President, Mahmoud Abbas, since taking office, as grieving relatives gathered here to mourn the two latest civilian victims, Fatima Ahmed, a 37-year-old pregnant mother of two small children, and her brother Zakaria, 45.

The siblings were killed by an Israeli missile which had been launched in the second bungled attempt to assassinate militants in less than 24 hours. The attack wounded 13 other members of the family, including six children, and partly wrecked the house in which they had all been concluding a celebratory meal in honour of Mr Ahmed, who had been on a week-long visit from Saudi Arabia to see his 83-year-old mother.

A pile of fallen masonry and a gaping hole in the house's straw roof were still visible yesterday at the house, about 20 metres from the main Salahadin north-south Gaza road at the entry to Khan Yunis.

The Israeli Defence Forces say that the attack early on Wednesday evening was aimed at a pick-up truck carrying members of militant Palestinian Resistance Committees. Witnesses said a six-inch crater on the other side of the road from the house was from a second missile.

The dead victim's sister-in-law, Amtiaz Ahmed, 47, described how she had been in the kitchen preparing coffee and tea at the end of the meal when the missile struck. Displaying a dozen shallow cuts on the back and arms of her 15-month-old nephew, Ahmed Sufian Ahmed, which she said were from shrapnel, Mrs Ahmed exclaimed: "Is he a terrorist? Does he have a rocket-propelled grenade? It is the Zionists who are the terrorists."

Three children were killed in an assassination attempt designed to curb Qassam rocket attacks from Gaza on Israel on Tuesday.

Mr Olmert said last night in Caesarea: "I am deeply sorry for the residents of Gaza, but the lives, security and well-being of the residents of Sderot [the Israeli border town which has borne the brunt of Qassam attacks] is even more important. I reject the attacks on the IDF and its commanders. No one is more dedicated or more cautious, and will continue to be so in the future." Kofi Annan, the UN secretary general, this week called on Israel to ensure its responses were "proportionate and do not put civilians at grave risk ". Almost three times as many Palestinian civilians have been killed in Gaza in the past nine days as Israeli civilians in Sderot killed by Qassam rockets in the past five years.

Maj-Gen Eliezer Shakedi, the Israeli air force commander entrusted with investigating how the civilian deaths occurred, told Army Radio: "We have to make a great effort to try everything possible to avoid hitting civilians." But he added: "We have to fight terrorism and we are doing it... This is... the most accurate and the best possible option without launching a broad and very significant [ground] operation."

The dead woman's husband, Nidal Wahba, 39, said the couple's 18-month-old son Khaled was in hospital after having emergency surgery for injuries to his head. With heavy irony, he added: "He has been shooting rockets at Amir Peretz", the Israeli Defence Minister who lives in Sderot.

But Mr Wahba, who works for an aluminium fabrication firm, said he wanted to see an end to violence on both sides. "We are against all this. We don't want to teach our children violence. I wouldn't like to see this happen to Israeli people."

The attack came amid signs of progress in talks between Fatah and Hamas designed to reach an agreement on a two-state solution to the conflict with Israel. Mr Wahba said: "There are people in Gaza who want to make war against Israel and people who want to make peace. I want the Palestinians to have one goal and that should be peace."

Of the missile strike which killed his wife and brother-in-law, he added: " I hope it will be the last one."