GAZA CITY: Sirens wailed across the Gaza Strip on Sunday as the still-devastated Hamas-ruled enclave marked one year since the start of Israel's deadliest offensive ever launched on the territory.

Events marking the anniversary began with sirens sounding at 11:20 am (0920 GMT), when the first bombs of Israel's "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.

"Gaza was steadfast and did not fall in this ugly, destructive war... And the resistance, which defended its land with honour, was not broken," he said.

"We call on all the sons of our people to unite and to take to the trenches of the resistance to face the criminal Zionist occupation."

North of Gaza City, hundreds of people carried pictures of the fallen past a UN school hit during the war and the flattened house of senior Hamas leader Nizar Rayan, killed in an air strike with his four wives and 10 children.

Hamas prime minister Ismail Haniya was to make a television address in the evening, with other events planned for the next 22 days, the length of the war.

On Saturday, December 27, 2008, Israeli warplanes launched simultaneous strikes on numerous Hamas targets throughout the territory of 1.5 million people, raids 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 left dead. Entire neighbourhoods of Gaza were flattened in the onslaught, which also wounded more than 5,500 people.

"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.

"The time has come now for unity and peace and justice and an end to the blockade," he said, referring to Israeli and Egyptian border closures that have sealed Gaza off from all but basic goods since Hamas seized power in June 2007.

The end of the war ushered in the calmest period in years along Gaza's borders as the ceasefires have held despite occasional violations by both sides.

The number of Palestinian rocket attacks in the year since the war has been 90 percent less than the one preceding it, according to Israeli figures.

But analysts warn that the calm around the borders belies busy preparations for the inevitable next round of bloodshed. Related articles: UN chief fears for Gaza

And Israel has come under intense criticism from the international community and human rights groups who have accused it of disproportionate force during the operation, including the use of white phosphorous in residential areas.

A UN Human Rights Council report released several months ago accused both Israel and Palestinian militants of committing war crimes during the offensive.

UN Secretary-General Ban Ki-moon on Sunday warned that "neither the issues that led to this conflict nor its worrying aftermath are being addressed."

"There is a sense of hopelessness in Gaza today for 1.5 million Palestinians, half of whom are under 18. Their fate and the well-being of Israelis are intimately connected," he added.

The Jewish state has also faced withering criticism over the blockade, which has made it virtually impossible to import materials for postwar reconstruction.

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 agency for Palestinian 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.