Tensions between Hamas and Fatah mounted over the weekend as the Islamist movement organized demonstrations in the Gaza Strip against the Palestinian Authority in the West Bank. The tensions have seen an ongoing crackdown on Hamas supporters in the West Bank by PA security forces loyal to Mahmoud Abbas. Fatah, on the other hand, accused Hamas of detaining dozens of its supporters and activists in the Gaza Strip over the past few days. Addressing the demonstrators in Gaza City, Khalil al-Hayeh, a senior Hamas official, called on his followers in the West Bank to resist attempts by Abbas's men to arrest them. "We won't abandon our people in the West Bank to be tortured by the security forces belonging to the Ramallah leadership," he said. The Hamas official also warned Fatah supporters in Gaza against any attempt to cause trouble. Hamas representatives in the Strip said Abbas's forces had detained more than 500 Hamas supporters and members in the West Bank over the past five weeks. They said that among those detained over the weekend was Baker Mansour, 17, the son of prominent Hamas political figure Jamal Mansour, who was killed by an IAF missile in a Hamas command center in Nablus in July 2001. Abbas's forces also arrested Ra'fat Nassif, a top Hamas operative in the northern West Bank, the Hamas representatives said, adding that the man had been involved in efforts to achieve reconciliation with Fatah. Hamas leaders claimed that Abbas's latest clampdown on their supporters in the West Bank was being carried out on instructions from Israel and the US. "This campaign is part of the security understandings reached between Abbas, on the one hand, and the Israelis and Americans on the other hand," said Osama Hamdan, the Hamas representative in Lebanon. "We have information that US army generals are supervising the campaign against Hamas." Hamdan said the stepped-up measures in the West Bank were aimed at "undermining" the movement and removing it from power after it won the 2006 parliamentary election. "Attempts to reverse the results of the free  election will fail," he said. "In fact, these attempts have backfired and Hamas remains the preferred choice of the Palestinians." Mahmoud Zahar, the top Hamas leader in the Gaza Strip, condemned Abbas and his PLO colleagues as "traitors and spies." If Hamas ever decided to join the PLO, it would be only to "cleanse the organization of all the traitors, spies and merchants," he said. Zahar said the only reason Abbas had agreed to attend the "national reconciliation" conference that was supposed to be held in Cairo last week was because he wanted to win Hamas's approval for the extension of his term in office for another year. Abbas and Fatah, he added, were very worried by the growing power of PA Prime Minister Salaam Fayad, of the independent Third Way party, whose government has laid its hands on the funds and security forces in the West Bank. "They feel that Salaam Fayad is a big threat and that's why Fatah wants to get rid of him," he said. "The Fatah people were hoping that Hamas would help them get rid of Fayad by agreeing to form a Fatah-Hamas unity government and keeping Abbas in power after January 2009." Hamas spokesman Fawzi Barhoum attacked Abbas for agreeing to hold another meeting with Prime Minister Ehud Olmert this week. Abbas was going to Jerusalem "to receive orders from Israel to keep trying to eliminate Hamas," he said. Barhoum said the Americans and Israelis had been putting heavy pressure on Abbas to refrain from solving the crisis with Hamas. Ahmed Abdel Rahman, a senior Fatah official and close aide to Abbas, scoffed at the Hamas allegations and said it was only a matter of time before the Hamas leaders found themselves on trial for staging a coup against the PA in the Gaza Strip. Abdel Rahman described the Hamas leaders as "highway thieves" and "mercenaries" who didn't represent anyone. "What does Hamas have to offer the Palestinians other than more militias that are persecuting and killing our people?" he asked. "The Hamas leaders are all murderers who are perpetrating crimes against our people. In one day they killed 13 members of the [pro-Fatah] Hilles clan."