The invitation, which was issued by King Abdullah bin Abdel Aziz, is the first of its kind and signals the Saudi government's concern over the growing involvement of Iran and Syria in Palestinian affairs.

In Nablus, the largest West Bank city, Fatah gunmen kidnapped 10 Hamas members and demanded the resignation of PA Interior Minister Said Siam of Hamas and the dismantlement of Hamas's "Executive Force" in the Gaza Strip.

"Iran and Syria are encouraging Hamas to continue fighting against Fatah," said a senior official in PA Chairman Mahmoud Abbas's office. "They want to deliver a message to the Americans that there will be no stability in Palestine, Iraq and Lebanon as long as Washington continues to ignore Syria and Iran."

Another PA official said the leaders of Iran and Syria were also responsible for the failure of talks between Fatah and Hamas over the formation of a Palestinian unity government.

"They are putting heavy pressure on Hamas not to make any concessions that would facilitate the formation of a unity government," he said. "They are trying to undermine US allies in Palestine, Iraq and Lebanon."

Members of Fatah's armed wing, the Aksa Martyrs Brigades, kidnapped 10 Hamas activists in Nablus, including Sheikh Fayyad al-Aghbar, a member of the city's municipal council.

Eyewitnesses said Aghbar was snatched by dozens of Fatah gunmen as he waited in line inside the local branch of the Arab-Islamic Bank.

The Fatah gunmen also raided the local offices of the Hamas-run Education Ministry and kidnapped five employees affiliated with Hamas. The attackers destroyed furniture and equipment inside the offices, the eyewitnesses said. A man who tried to prevent the gunmen from kidnapping his relative, who is also a Hamas member, was shot in the legs, they said.

The gunmen issued a statement demanding the resignation of Siam and the dismantlement of Hamas's security force in the Gaza Strip. They accused Aghbar of issuing orders to Hamas gunmen in the West Bank to shoot Fatah members. The statement said the hostages were senior Hamas leaders in Nablus.

During an emergency meeting of the Hamas-led government in Gaza City, PA Prime Minister Ismail Haniyeh urged Palestinians to abandon violence and endorse dialogue as the only means for solving differences. He appealed to Abbas to order all militiamen to withdraw from the streets and to remove security checkpoints set up in many areas in the Gaza Strip.

"Palestinian society does not need to be further militarized," Haniyeh said. "The Interior Ministry alone is responsible for restoring law and order."

Ahmed Abdel Rahman, a senior Abbas aide, responded by holding Haniyeh's government responsible for the latest deterioration because of its failure to respect the law and democracy.

"No one in Hamas has the right to shed alligator tears," he said. "They are sending death squads to attack and destroy the homes of residents in the Gaza Strip."

Abdel Rahman launched a scathing attack on Siam, accusing him of using the "Executive Force" to kill Palestinians.

"Where in the world do you have an interior minister who establishes a 5,000-strong force and orders it to kill anyone he chooses?" he asked. "How can a responsible man like Siam describe Fatah as a Zionist-American pawn?"

Abdel Rahman said Hamas had deployed dozens of snipers on rooftops in the Gaza Strip to kill civilians and attack public institutions.

"National dialogue is the only alternative to the dialogue of bullets," he said. "It is also an alternative to killing children."

Egyptian security officials based in Gaza City met Sunday with Haniyeh and Fatah leaders in a bid to end the fighting amid reports that Cairo had threatened to halt its mediation efforts because of the latest flare-up.

Sources in Gaza City told The Jerusalem Post that the Egyptian officials, Burhan Hamad and Ahmed Abdel Khalek, delivered a warning to the two parties from Egyptian General Intelligence chief Omar Suleiman to the effect that Cairo would suspend its efforts if the fighting continued.