GAZA CITY (AFP) - Sirens wailed across the Gaza Strip on Sunday as the still devastated Hamas-ruled enclave marked one year since the start of Israels deadliest offensive ever launched on the territory. Anniversary events began with the sirens at 11:20am (0920 GMT), when the first bombs of Israels Operation Cast Lead, launched in a bid to halt years of rocket fire from the enclave, slammed into the coastal strip. Senior Hamas leader Ahmed Bahar struck a defiant tone, saying the will of the steadfast and the resistance was victorious at a ceremony unveiling a war memorial with the names of hundreds of Palestinians killed in the fighting. The resistance, which defended its land with honour, was not broken, he said. North of Gaza City, hundreds of demonstrators carried pictures of the fallen past a UN school hit during the war and the home of Nizar Rayan, a senior Hamas leader killed in an airstrike along with his four wives and 10 children. On December 27, 2008, Israeli warplanes launched a wave of raids across Gaza that killed at least 225 people in what was one of the bloodiest single days in the decades-long Israeli-Palestinian conflict. The war ended 22 days later with mutual ceasefires by Israel and Hamas, with some 1,400 Palestinians, including more than 400 minors, and 13 Israelis killed. Another 5,500 people were wounded in the onslaught. Those were dark days. There was killing in every street and alley, said Dr Muawiya Hassanein, the head of Gaza emergency services. Sixteen of his paramedics were killed as they struggled to collect the wounded. We are developing our capacities to match the Zionist escalation, and it is our right as the Palestinian resistance to develop and acquire whatever weapons we can, Abu Obeida, a spokesman for the armed wing of Hamas, told reporters. We are ready to confront any new aggression with all our power, he added. The war and the blockade have also drawn criticism from the Western-backed Palestinian Authority, with President Mahmud Abbas on Sunday vowing to pursue Israeli war criminals. We are determined to go after the war criminals that committed the most heinous and atrocious crimes against our children and women and elderly and our innocent youth, the Western-backed leader said in a statement. This anniversary calls on us to criticise this aggression and these crimes in the strongest terms, he added. Some 6,400 homes were severely damaged or destroyed during the war, according to UN figures, as well as several large factories and farms. Most of the tens of thousands of people who lost homes now share crowded apartments with relatives or huddle under tents supplied by aid groups, and the UN Relief and Works Agency for Palestine refugees (UNRWA) has started building homes out of mud bricks because of the shortage of concrete. Gaza has been bombed back to the mud age, not the stone age, UNRWA spokesman Chris Gunness said.