(JTA) — Palestinian “heroes” are digging tunnels to be used in future attacks on Israel, Hamas’ senior political leader said. At a funeral in Gaza City Friday for seven Hamas operatives killed when rain and flooding caused a tunnel they were working on to collapse, Ismail Haniyeh said preparations are underway for the next confrontation with Israel. “East of Gaza City, heroes are digging through rock and building tunnels, and to the west they are experimenting with rockets every day,” Haniyeh said. “The resistance continues on its path of liberation of the land.” Thousands of people attended the funeral, with many chanting slogans urging violence against Israel.

According to the Times of Israel, Hamas has more than 1,000 people working around the clock, six days a week, digging tunnels, which are lined with concrete and are “being dug 30 meters deep, with sophisticated engineering equipment and more advanced technological support, including engineers’ blueprints.” Hamas’ vast network of tunnels, many leading into Israel, was a major issue during Operation Protective Edge, Israel’s 2014 war in the Gaza Strip. During the war, Israel destroyed more than 30 tunnels, which were used to smuggle weapons, as well as stage terrorist attacks and kidnappings inside Israel.

Last week, the head of Israel’s Eshkol Regional Council, near the Gaza border, reported that residents of Moshav Pri Gan can hear and feel the tunnel digging below. Israelis near the border remain vulnerable, because the IDF still has not built protective barriers to block cross-border tunnels.