GAZA CITY, Gaza Strip (AP) — Thousands of Palestinians staged a sixth weekly protest Friday near Gaza's border with Israel, some throwing stones and burning tires as Israeli soldiers fired live rounds and volleys of tear gas from across the border fence.

Gaza's ruling Hamas group, which has organized the marches, has said the protests might culminate in a mass breach of the border fence later this month.

By late afternoon Friday, at least 40 protesters had been hurt by live fire or tear gas, according to Gaza health officials who did not provide a breakdown. Since late March, 39 protesters have been killed and more than 1,700 wounded by Israeli fire.

At one of the protest sites, activists burned tires sending plumes of black smoke billowing into the air.

Over loudspeakers, Israeli soldiers told those burning tires that they could be targeted. "You: Stop bringing tires!" said the announcement from across the fence. "The tires cause shootings."

Along the border area, Palestinians assembled after Muslim noon prayers at five protest camps set up several hundred meters from the fence. Some moved closer to the fence, throwing stones with slingshots and burning tires. Israeli soldiers fired live rounds and tear gas.

The Islamic militant group Hamas has called for mass rallies at the border every Friday, as part of a weeks-long campaign of protests against a decade-old blockade of the territory. The protests are also driven by widespread desperation over the blockade-linked hardships of life in Gaza, where two thirds of young people are unemployed and electricity runs for only a few hours a day.

Yehiyeh Amarin, an 18-year-old protester, was among nearly two dozen activists rolling tires toward the fence on Friday to set them ablaze. His face partially covered with a black-and-white "keffiyeh" scarf, he's part of a group of young protesters calling themselves "the tires unit," responsible for collecting and burning old tires along the border.

"If no solution happens by May 15 we will continue the protests or we die," said Amarin, as another protester behind him brandished a yellow wire cutter. "We will cut through the fence."

He said he and his friends spend their weekdays collecting tires for the weekly protests.

"We want a dignified life and a return to our lands," he said.

The mounting casualty toll has led to growing criticism of Israel. Rights groups say Israeli open-fire regulations are unlawful because they permit troops to use potentially lethal force against unarmed protesters. Israel's Supreme Court is currently weighing a petition by six rights groups to restrict or ban the use of live fire on the border.

The European Union and the United Nations have also criticized the use of lethal force against the protesters.

Israel says it's defending its sovereign border, including nearby communities, and that soldiers only target instigators. It accuses Hamas, sworn to Israel's destruction, of trying to carry out attacks under the guise of the mass protests. It has said that some of those protesting at the border over the past few weeks tried to damage the border fence or plant explosives along it. Others have hurled improvised explosives, firebombs, or flown kites attached to burning rags to set Israeli fields on fire.

The marches are part of what organizers say is an escalating showdown with Israel, to culminate in a mass march on May 15 — the day Palestinians commemorate their mass uprooting in the 1948 war over Israel's creation. Hundreds of thousands of Palestinians fled or were driven from homes in what is now Israel. Two-thirds of Gaza's two million residents are descendants of refugees.

Hamas says the protests are aimed at breaking the border blockade and pressing for the "right of return" of displaced Palestinians and their descendants. The blockade was imposed by Israel and Egypt after Hamas seized Gaza in 2007, a year after winning Palestinian parliament elections.

Hamas officials have given conflicting statements about a possible mass border breach on May 15.

Israel has warned that it will prevent such a breach at any cost.