Israel has stepped up its campaign to enforce a buffer zone in the northern Gaza Strip. Army helicopters have fired missiles into two office buildings in Gaza City.There are no reports of casualties. A third missile was also aimed at a road in northern Gaza, creating a massive crater. The Israeli Army claimed the offices targeted were used by an armed group belonging to the Palestinian Fatah faction. Israel’s withdrawal from Gaza after 38 years has not stopped rocket attacks by Palestinian militants. In recent days, some have landed close to farming communities. Defiant Palestinian militants insist they will step up the attacks if the air strikes continue. The makeshift rockets fired by Gaza militants rarely cause casualties. But they could lead to political fallout. Prime Minister Ariel Sharon is campaigning for re-election on the strength of the Gaza pullout. He claimed the move would boost Israel’s security. Further attacks could undermine Sharon’s campaign and bolster support for his right-wing opponent Binyamin Netanyahu, who denounced the withdrawal as a surrender.