In striking at Palestinians in Gaza and the West Bank Sharon is seeking not only to hobble Hamas's chances in January's legislative elections but to enhance his own domestic political standing, reports Khaled Amayreh in Jerusalem For the fifth day running Israel launched air strikes on mainly civilian targets throughout the densely-populated Gaza Strip. The escalation came despite an announcement by Hamas that it would refrain from firing missiles on Israeli settlements. Yesterday, Israel escalated its offensive using artillery for the first time. On Tuesday Israeli F-16 fighter jets hit three bridges in northern Gaza and bombed houses in Khan Younis, south of Gaza City. The bridges, claimed an Israeli army spokesman, had been used to fire homemade rockets at Israeli settlements and military targets. "Our aircraft attacked three bridges in the Bait Hanoun sector, in the northern Gaza Strip, which enabled terrorists to reach sectors from where it was possible to fire Qassam rockets at Israel," said an Israeli spokesman. In Beit Hanoun at least one Palestinian was injured and two buildings damaged. A Palestinian security spokesman dismissed Israel's claims. According to the logic of the Israeli army, he said, Israel can destroy every road in Gaza on the grounds that they might be used by the resistance. "These are irrational justifications. They [Israel] are destroying homes, schools and bridges, impoverishing the Palestinian people and exacting revenge for their withdrawal from Gaza," said Hassan Hilles, a Palestinian security spokesman. On Sunday Israeli warplanes partially destroyed a school in downtown Gaza. Al-Arkam school, which also served as a community centre, was founded by Sheikh Ahmed Yassin, Hamas's spiritual leader assassinated by Israel in Gaza two years ago. The following day pupils and teachers began to clear the rubble of the school which the Israeli army said it had targeted to undermine the "material and psychological infrastructure" of Hamas. At least 15 civilians were injured in the school bombing, including a 40-day-old baby, and several nearby homes were damaged. Earlier the Israeli army had launched several targeted assassinations against members of Hamas and Islamic Jihad's armed wings, the Izzidin Al-Kassam and Al-Quds regiments. At least three Hamas resistance fighters were killed, as well as Islamic Jihad leader Mohamed Khalil whose car was hit by a missile fired from an Apache helicopter as it travelled along the coastal road south-west of Gaza City. Israel said the assassinations were a reprisal for the firing of 35 Qassam missiles at the settlement of Sderot, north-east of Gaza. The missiles caused minimal damage, and on Sunday Hamas announced that there would be no more. It did not, said Hamas, want to give Israel a pretext to slaughter more Palestinians. The latest round of violence began on Friday when a blast killed 16 people, including a number of Hamas fighters, during a rally at the Jabalya refugee camp north of Gaza. Eighty others were injured, including a number of children. Hamas blamed Israel for the bombing, claiming an Israeli helicopter had fired a missile at a vehicle, triggering the huge explosion. Israel denied any responsibility while the PA said the blast was the result of the mishandling of explosives by Hamas. It is not yet clear whose version is true, a picture further muddied by the suggestion of some neutral Palestinian sources that Israeli collaborators may have been behind the detonation. The Jabalya blast, said one Hamas insider, has generated "confusion" within the movement. "I think we were carried away by the Israeli withdrawal and we are paying the price for this now," said a Hamas leader, speaking to Al-Ahram Weekly on condition of anonymity. He was critical of the movement's decision to organise military parades and announce the identity of resistance leaders. "That was wrong. We only give our enemies PR ammunition with which to attack us. We need to review such tactics." Meanwhile, in an apparent effort to disrupt upcoming Palestinian elections, the Israeli army continued to arrest hundreds of Palestinian activists throughout the West Bank. Palestinian sources said Israeli troops had detained 82 Islamist activists, mainly in the Al-Khalil and Bethlehem areas. The detainees include university professors, school teachers, doctors, business people and students. Many of the detainees had already signalled their intention to stand as candidates in the legislative elections scheduled for January. One detainee told Al-Ahram Weekly he had been asked by a senior Shin Bet official to formally state his intentions not to stand in return for his release from detention. Israel's Prime Minister Ariel Sharon said last week he would seek to disrupt the elections if the Islamic resistance group, Hamas, took part without abandoning its anti-Zionist platform. Israel's Foreign Minister Silvan Shalom has made similar threats, leading many observers to conclude that the current arrests are part of a concerted campaign to stop Hamas from contesting the elections. On Sunday a further 207 activists were arrested, and on Monday 90 more, including civil servants and at least three journalists. Israel already holds 10,000 Palestinian prisoners, many without charge or trial. It is as yet unclear how long those arrested this week will be detained, and whether or not they will face charges. In addition to disrupting elections, Israeli Prime Minister Ariel Sharon is also keen to demonstrate to Likud members, many of whom opposed the withdrawal from Gaza, that there has been no softening in his position. It is unlikely to be a coincidence that the latest onslaught against Palestinians, the military assault in Gaza and the sweeping arrests in the West Bank, coincided with a crucial Likud vote over primary elections that will determine whether or not Sharon survives as Likud chairman. Sharon won Monday's vote by the narrowest of margins, with 51 per cent of Likud central committee members backing his position, and 49 per cent voting against.