Palestinian President Mahmoud Abbas, defying the rival Hamas group that controls the Cabinet and parliament, announced Saturday a July 26 referendum on the establishment of a Palestinian state alongside Israel.

Hamas immediately rejected the referendum, which is expected to have a clear majority. Abbas' announcement followed renewed fighting between Hamas and Abbas loyalists in Gaza and a deadly Israeli artillery strike that led Hamas to call off a 16-month-old truce.

"We have to rule out the idea of a referendum and this is what I will tell Abu Mazen," Palestinian Prime Minister Ismail Haniyeh of Hamas said, calling Abbas by his nickname.

CountryWatch: Israel

Abbas said the vote could be called off at any time before July 26 if the sides reach agreement on the document. Written by prominent Palestinian militants jailed by Israel, the document calls for a Palestinian state in the West Bank and Gaza, lands Israel captured in the 1967 Mideast war, an implicit recognition Israel.

Later Saturday, Abbas and Haniyeh met in Gaza along with Interior Minister Said Siyam, also of Hamas.

In a speech Saturday, Abbas denounced an Israeli artillery attack a day earlier that killed eight civilians, many from the same family, who were enjoying a weekend picnic on Gaza's beach.

He brushed off Hamas' call to put off the vote due to the renewed violence, saying acceptance of the referendum would help the Palestinians achieve their dream of statehood and bring an end to a debilitating international aid boycott imposed after Hamas' rise to power.

"When we reach an agreement over the prisoners document, the siege will end," Abbas said. In the referendum, Palestinians will be asked to vote "yes" or "no" on the document, which polls show has wide support among Palestinians, partly because of the clout of its imprisoned authors.

Accepting the document could give Hamas, which is officially sworn to Israel's destruction, an avenue for moderating its militant ways.

But so far Hamas has held firm to its refusal to recognize Israel, renounce violence or accept past peace accords — conditions set by Israel and the international community for doing business with the Islamic group.

The unsuccessful negotiations between Abbas and Hamas over the document have laid bare divisions between Hamas' local and Syria-based leadership, with the latter, led by militant Khaled Mashaal, holding sway.

However, the economic stranglehold, which has prevented the new Hamas-led government from paying three months of salaries to its 165,000 employees, could bring the Islamic group to its knees.

Abbas' declaration on Saturday followed through on an ultimatum he gave late last month, in which he gave the Palestinian factions 10 days to accept the prisoners' document or go to a referendum. Earlier in the week, Abbas extended that deadline by several days.

Tensions between Abbas and Hamas have been increasing since the Islamic group, which won a January parliamentary election, took power in March.

Abbas, elected separately last year, still wields considerable authority. Fatah and Hamas are in tough battle over control of the security forces, leading to factional fighting in Gaza's streets that has raised the specter of civil war.

In the hours before Abbas' announcement, new violence erupted between gunmen loyal to the president and Hamas' militia.

Gunmen shot and killed a 39-year-old Palestinian security officer in a botched kidnapping attempt, the Palestinian Preventive Security said. The force, loyal to Abbas, accused Hamas of the killing and vowed to impose justice.

During the funeral procession for Maj. Bassam Qutub, a gunbattle erupted between gunmen from Hamas and the Preventive Security force. The car of Gaza's top pro-Abbas general, Rashid Abu Shbak, was caught in the crossfire, and he had to be rushed out of the area while under fire.

Four people were wounded in the fighting, one of them seriously, hospital officials said. Hamas gunmen took up positions in the area, leading to a tense standoff.

Hamas also claimed responsibility Saturday for firing at least 15 rockets at Israel, as well as a barrage of mortar bombs — essentially ending its 16-month truce. However, it was not clear if Hamas would stick to that position, since as a governing power it has much to lose by confronting Israel.

The army said more than two dozen homemade rockets and mortar shells were fired at Israel on Saturday. No casualties were reported in the attacks.

The Israeli artillery attack on Friday killed eight civilians, including two babies. Abbas condemned the strike as a "genocidal crime." Haniyeh called the shelling a "war crime" and called for an end to Hamas-Fatah fighting.

Israel's army chief expressed regret for the killing of civilians, but stopped short of accepting responsibility for the incident. Lt. Gen. Dan Halutz said an investigation was still underway, and it was still not clear what caused the deaths.

The investigation had so far ruled out gunboats and an airstrike, but it is still possible Israeli artillery or even a misfired Palestinian rocket caused the deaths, Halutz said.