The Israeli Defense Forces on Sunday claimed that it has uncovered the biggest tunnel constructed by the Palestinian militant group Hamas in Gaza, just a few hundred metres from a key border crossing.

“This massive tunnel system branches out and spans well over four kilometres,” the Israeli Defense Forces tweeted. “Its entrance is located only 400 meters from the Erez Crossing, used by Gazans on a daily basis to enter Israel for work and medical treatment in Israeli hospitals.”

The Israeli Army alleged that the tunnel may have facilitated the transit of vehicles, militants and supplies for the October 7 attack, reported the Associated Press.

On October 7, the Hamas militants had used a rocket-propelled grenade to cross the portion of the wall close to the Erez crossing, the Israeli Army said. The militants had killed at least three soldiers and took 240 hostages back to Gaza on the day.

The attacks had also killed around 1,200 persons ensuing Israel’s unprecedented attack on Gaza killing 18,000 residents in the Palestinian territory.

The entrance to the tunnel is a few hundred metres from the heavily fortified Erez crossing and an Israeli military base, according to the Army. The floor of the tunnel is compacted earth, while its walls are reinforced concrete and the entrance is made of a metal cylinder with 1.5 centimetre thick walls, reported AFP.

The passageways also include drainage and sewage systems, electricity, ventilation and a communication network as well as rails. According to AFP, a small vehicle could also be used to travel through the tunnel.

The Israeli Army claimed that the tunnel system was a project led by Mohammad Sinwar, the brother of Hamas leader Yahya Sinwar, and the commander of Hamas’ Khan Yunis Battalion.