At least 300,000 Palestinians rallied in Gaza City on Saturday to mark the 20th anniversary of Hamas's founding, as deposed Palestinian prime minister Ismail Haniyeh promised Hamas would not succumb to international pressure.

The central square in Gaza City was awash with green flags and dozens of armed, masked men from the group's military wing patrolled. Some estimates put the crowd as high as 500,000.

"The message from you today is that Hamas and these masses will not yield before the sanctions," Haniyeh told the cheering onlookers. The crowd shouted in response, "To you, we come Haniyeh."

"Today is the day of Jihad, resistance and uprising," he said. "Those who remain committed to the constant rights of their people, those who make an enemy of America and the Zionist occupation [Israel] gain popularity. This is Hamas."

Haniyeh lambasted the renewal of peace talks between Israel and Palestinian President Mahmoud Abbas' administration in the United States last month, warning they will not bring about a cessation of Israeli settlement construction or yield any other Israeli concessions.

"As for the fruits of the other track, the track of negotiations, normalization and bargaining, all can see that it is the consolidating of settlements ... injustice and oppression for the Palestinian people," Haniyeh said. "It is bitter fruits."

The Hamas leader warned Abbas against conceding in peace talks on the Palestinian demand that refugees who fled past wars with Israel and their descendants be allowed to return to their homes. Their fate is a key sticking point in the talks that are meant to iron out a final peace agreement.

"There is no such thing as a just solution to the right of return," Haniyeh said. "It is the right of every refugee ... to return to the land."

Meshal: Palestinians can launch more intifadas Hamas' Damascus-based political leader Khaled Meshal threatened Saturday to launch a new intifada against Israel, warning in a 20th anniversary message to Hamas TV that Hamas would not abandon violence.

"This is our real choice, our trump card, which causes the enemy to succumb to us," he said. "Our people are able to launch a third and fourth uprising until the dawn of victory arrives."

Meshal said Abbas, who controls the West Bank, does not have the mandate to negotiate with Israel.

Addressing the rally, senior Hamas official Mushir al-Masri warned Israel to expect many casualties if Israel Defense Forces troops launch a major operation in the coastal territory in an attempt to stop almost daily rocket fire by militants at Israel.

"Jews, go back, because we have already dug graves for you," Masri said. Israel carries out regular raids on Gaza and has killed dozens of militants in the past month.

This week, IDF Chief of Staff Gabi Ashkenazi said a major incursion into was becoming more likely. "We will come to the point where we will have to carry out the big operation," he said.

Large pictures of Hamas' leaders, both in Gaza and in exile, were draped across the speakers' podium. A black banner hanging from a nearby building read, in Arabic, English and French: "We will not recognize Israel."

"This is the real referendum on the popularity of resistance, the people converging behind Hamas," said Zayed Herzallah, a 28-year old merchant, who brought a van full of young relatives. "Hamas today, after 20 years and after thousands of martyrs, is graduating the fourth generation (of supporters)."

In the crowd were about 50 female members of Hamas' military wing, dressed in long robes and sporting military-style ammunition vests. Some covered their faces with veils, others with ski masks. Several took to the stage, waving green Hamas flags.

Hamas says PA detained 26 of its supporters in West Bank Also Saturday, Hamas said Palestinian security forces loyal to Abbas had arrested 26 of its supporters in the West Bank.

"The Palestinian security forces continued the detention campaign that targets Hamas supporters in various cities in the West Bank," Hamas said in a statement faxed to the press.

The statement added that most of the detainees were arrested in the town of Qalqilya.

"The arrests are meant to prevent Hamas from marking its 20th anniversary," the statement said.

Hamas' anniversary rally comes amid heightened tensions between the two main Palestinian factions. On Friday, Hamas police arrested Omar Al-Ghoul, an adviser to Abbas' prime minister, Salam Fayyad, and seized some of his belongings.

Al-Ghoul was the most senior Fatah politician to be detained since Hamas forces overtook the territory in June.

Also Friday, three people were killed in a mysterious explosion at a Fatah-organized funeral in Gaza City. Witnesses said a man carrying explosives in a jacket accidentally detonated them, while Hamas security said a member of the procession threw a pipe bomb.

Fatah quickly accused Hamas of being behind the explosion, and the Ramallah government announced Saturday a national day of mourning. Hamas denied involvement, and issued orders to question another senior Fatah official in Gaza, Ibrahim Abu Naja, accusing him spreading the rumors. As of Saturday, Abu Naja was not in detention.