GAZA CITY, Gaza Strip, (AP) -Dozens of gunmen attacked a training base of Mahmoud Abbas’ Presidential Guard before dawn on Sunday, killing a member of the elite security force and sparking a fierce gunbattle, just hours after the Palestinian leader announced he would end nine months of Hamas rule by calling early elections.

Sending a strong message to Hamas, Abbas called a meeting early Sunday with the Central Election Commission — the first step toward holding early elections. The meeting indicated that Abbas is determined to move ahead quickly with the balloting, despite Hamas’ strong objections.

Sunday’s assault, blamed on Hamas, marked a new stage in escalating fighting between Hamas and Abbas-allied security forces. The attackers carefully planned it, cutting power to the camp first, and chose a highly symbolic target.

The gunmen set fire to trailers and tents. Only about a dozen guardsmen were in the camp, located about 700 yards from Abbas’ office and residence. The assailants fled after reinforcements were sent to the base from other Presidential Guard camps. Abbas was in the West Bank at the time.

Hamas denied involvement, but security officials said the attackers were from the Islamic militant group. The assault came several days after Hamas accused a top Abbas ally, Gaza strongman Mohammed Dahlan, of being behind a shooting attack on the entourage of Prime Minister Ismail Haniyeh of Hamas.

Dahlan, who has denied involvement, was to return to Gaza from the West Bank on Sunday, but postponed the trip without reason.

Also Sunday, members of the Presidential Guard took over the rooftops of the Hamas-controlled Agriculture and Transportation ministries in Gaza City. There were no reports of violence, but Hamas officials said the takeover was part of Fatah’s attempts to overthrow it. Fatah officials said they were merely trying to maintain security; Abbas’ Gaza residence is located nearby.

In response to Abbas’ call for early elections, Hamas had urged its supporters to take to the streets in protest. On Saturday evening, thousands of Hamas loyalists marched across Gaza and 18 Palestinians were wounded in clashes between the two political camps.

In seeking early elections, Abbas took a bold gamble that could end up driving the Palestinians toward all-out civil war, strengthen Hamas and further put off peace efforts with Israel.

Hamas accused Abbas of trying to topple its government and promised to block the elections. “This is a real coup,” said Foreign Minister Mahmoud Zahar, a Hamas hard-liner.

Hamas’ landslide election in January parliamentary elections split the Palestinian leadership into two camps. One, led by Abbas, seeks peace with Israel; the other, led by Hamas, is sworn to the Jewish state’s destruction. The infighting has often degenerated into violence, and last week, tensions reached their highest peak in years.

Abbas tried to end the power struggle by bringing Hamas into a more moderate coalition with his Fatah Party, but Hamas refused to pay the price he demanded — recognizing Israel and renouncing violence.

“We have a crisis. We have an authority with two heads. So what do we do? Bullets or ballots?” asked Saeb Erekat, an aide to Abbas. “Abu Mazen said ballots,” he said, using Abbas’ nickname.

Across the West Bank and Gaza, streets were largely deserted Saturday as everyone watched Abbas’ 90-minute address, peppered with criticism of Hamas.

Abbas said a unity government was still the best option, but that he had despaired of persuading Hamas to enter into a coalition with Fatah. The Hamas government has drawn crushing international sanctions over its anti-Israel stand, but has still refused to recognize Israel, the West’s condition for resuming aid.

“I … decided to call for early presidential and parliament elections,” Abbas said from his West Bank headquarters, after outlining months of failed coalition talks. “Let us return to the people, to hear their word, and let them be the judge.”

His aides said they expected the vote to be held by the summer. His talks with the Central Election Commission will focus on how much time is needed to prepare. Hamas claims Abbas does not have the authority to call new elections.

Abbas, 71, was elected president in 2005. If he does not run again — he has said he would not seek another four-year term — Palestinian moderates would not have a strong candidate.

Hamas, if it decided to participate in any election, could field Haniyeh, the prime minister, who according to polls is the most popular politician after Abbas.

During times of political turmoil, any efforts to resume peace talks with Israel would likely be frozen. In recent weeks, Israeli Prime Minister Ehud Olmert has said he was willing to give up large parts of the West Bank in a peace deal, and that he was ready to talk peace.

Israeli government spokeswoman Miri Eisin said Olmert “respects Abu Mazen and hopes that he will have the capability to assert his leadership over the Palestinian people, and to bring about a government that will comply with the international community’s principles.”