Israel is not responsible for a blast that killed eight Palestinians enjoying a picnic on a Gaza beach last Friday, Defence Minister Amir Peretz says.
Palestinian PM Ismail Haniya visited the wounded in hospital
He said an inquiry had shown an Israeli shell could not have caused the blast, as had initially been alleged.
The Israeli probe is based on TV film of the aftermath and shrapnel taken from the injured treated in Israel.
A report by US-based group Human Rights Watch says the deaths were likely to have been caused by Israeli shelling.
Palestinian officials have also rejected the Israeli army's report.
The deaths of eight civilians on Friday - seven of whom belonged to the same family and three of whom were children - sparked worldwide condemnation of Israel.
United Nations Secretary General Kofi Annan has called for a full independent inquiry into the incident.
The speed with which Israel concluded its investigation underlines the sensitivity of the incident - but whether its findings change any minds is another matter, says the BBC's Nick Childs in Jerusalem.
The militant group Hamas, which heads the Palestinian government, ended an informal ceasefire and fired dozens of home-made rockets at Israel, causing panic and several injuries.
In an unrelated incident, a gunman from the al-Aqsa Martyrs' Brigade was shot dead by Israeli troops in the West Bank town of Jenin early on Wednesday morning.
The Israeli military initially said it regretted Palestinian civilian deaths and it suspended further shelling as an internal committee headed by General Meir Klifi investigated the incident.
The investigation focused on six artillery shells fired by the military. The army says it is certain five landed about 250 metres (820ft) from the beach where the Ghalia family were sitting.
Mr Peretz (right) said there was no proof Israel caused the blast
One shell apparently misfired, but the explosion which ripped through the Ghalia family's picnic was at least eight minutes afterwards, the army says.
Concluding his investigation, General Klifi said on Tuesday: "The chances that artillery fire hit that area at that time are nil."
Appearing alongside him, Mr Peretz said "the intention to describe this as an Israeli event is simply not correct".
But they did not say what might have caused the blast.
Israel frequently shells northern Gaza, targeting militant rocket crews who attack nearby Israeli territory.
There have been suggestions that a mine could have been planted on the beach to deter Israeli amphibious assaults.
But an expert working for the Human Rights Watch said the Palestinians' injuries were not consistent with a blast taking place beneath them.
"It has been suggested by some that the family was killed by a land mine, and this is patently not the case," Mark Garlasco said.
"All of the evidence is pointing to a 155mm shell as having killed and injured the Palestinians here on the beach," he said.
"My assessment [is] that it's likely that this was incoming artillery fire that landed on the beach and was fired by the Israelis from the north of Gaza."
Reacting to earlier reports that the Israeli inquiry would blame the blast on a mine planted by Hamas, a Hamas spokesman accused Israel of "shying away from its responsibilities over this atrocious crime".
"These Israeli allegations are false and lack any credibility," Ghazi Hamad said.