GAZA CITY, April 20, 2018 (News Wires) - Thousands of Palestinians joined the fourth weekly protest on Gaza's border with Israel on Friday, some burning tires or flying kites with flaming rags danglling from their tails. Two Palestinians were killed by Israeli troops firing from across the border fence, health officials said. Huge black plumes of smoke from the blazing tires engulfed the area, as Israeli troops fired tear gas and live bullets, witnesses told AP. Gaza's Health Ministry said 40 protesters were injured. The protests are part of what organizers, led by Gaza's ruling Hamas group, have billed as an escalating showdown with Israel, to culminate in a mass march on May 15. Organisers have made conflicting statements about whether they plan an eventual mass border breach. In the past three weeks, 28 Palestinians were killed and hundreds wounded by Israeli troops firing from across the border fence. In addition, two Palestinian men, ages 24 and 25, were shot and killed in a border area in northern Gaza, the Health Ministry said. Hamas says the protests are aimed at breaking a crippling border blockade that was imposed by Israel after the Islamic group overran Gaza in 2007, a year after winning Palestinian parliament elections. The marches also press for a "right of return" of Palestinian refugees and their descendants to what is now Israel. Hundreds of thousands of Palestinians fled or were forced from homes in the 1948 war over Israel's creation. Palestinians mark May 15, the anniversary of Israel's founding, as their "nakba," or catastrophe, to mourn their mass uprooting. "We will stay here until we reclaim our lands," said Ahmed Nasman, 21, speaking in a protest tent camp east of Gaza City, as activists near him prepared kites. "Every day, we will come here with a new way to resist them," he said, referring to Israel. Several thousand protesters flocked to the border area Friday, most gathering in five tent camps several hundred metres away from the border. Smaller groups advanced towards the fence, throwing stones, burning tires and flying kites with burning rags. The kites are part of a new tactic aimed at setting fields on the Israeli side on fire. Most kites were stitched together in the colours of the Palestinian flag. One white kite bore the Nazi swastika.