The Israeli army has said it has uncovered the biggest Hamas tunnel in the Gaza Strip so far, just a few hundred metres from a key border crossing.

Such was its size that small vehicles would be able to travel within the tunnel, an AFP photographer granted access to it reported.

The underground passage formed part of a wider branching network that stretched for more than 2.5 miles (4km) and came within 400 metres of the Erez border crossing, the army said.

Israeli forces said it would have cost millions of dollars and taken years to construct, and the project was led by Mohamed Yahya, the brother of the Hamas chief, Yahya Sinwar.

The honeycomb of passageways features drainage and sewage systems, electricity, ventilation and a communication network as well as rails. The floor is compacted earth, the walls are reinforced concrete and the entrance is a metal cylinder with 1.5cm thick walls.