Abu Jundal stands on a Gaza City street, unarmed and wearing civilian clothes. Only his black, multi-pocketed tabard and his beard give a hint of who he really is: a Hamas platoon commander having a day off in the middle of the war with Israel.

“We work in shifts, one day on, one day off, so we do not get exhausted,” he said, adding that his shifts run from 10pm until 5am every other night. His was one of three platoons operating in this sector of the northern Gaza Strip.

Ehud Barak, the Israeli Defence Minister, has promised “all-out war” against the Islamist movement, but Abu Jundal, 29, said that Hamas had so far thrown only a fraction of its 15,000-strong guerrilla force into the fray. At the current rate of attrition, he said, it could carry on the battle for another three months.

“We are only working at 10 per cent of our capacity. There is always somebody backing us up, held in reserve. There are different lines of defence,” he said, looking strained from days of fighting. Despite serving on the shifting front lines, Hamas fighters still have to provide for their families in their time off, as Gaza runs out of basic supplies of food and fuel.

He said that his unit had not yet seen close-quarters combat, having used only rocket grenades, landmines and mortars to try to halt the onslaught, in which Israeli officials claim have killed 130 Hamas fighters. “The Israelis are not coming on foot, they are mostly in tanks and using helicopters and drones,” he said.

To combat the superiority of Israel's US-funded war machine, Hamas has prepared a number of what the platoon leader called “surprises”. He refused to elaborate, but said that the key priority for him and his comrades was to kidnap Israeli soldiers in an attempt to use them as bargaining chips. Hamas already holds one Israeli corporal seized in a tunnel raid under the border in 2006.

“Our main aim is to capture as many Israeli soldiers as we can,” he said. “We'll do whatever we can to achieve this and to destroy the myth of the invincible Israeli army.”

Israeli security sources have described finding elaborate tunnel complexes running from houses and mosques, allowing Hamas to outflank Israeli forces, emerge with anti-tank rockets and to try to snatch soldiers who have strayed too far from their units.

Israeli media reported a capture attempt on the first day of the ground offensive, when a soldier from the Golani Brigade climbed into a tunnel that his unit had found underneath a house.

He ran into waiting Hamas fighters and fought a gunfight in which he was wounded as the guerrillas tried to capture him. The Israeli managed to flee back to his comrades, who blew up the tunnel.

“Until now, we have not faced any enemy worthy of our respect. Any army that concentrates on killing civilians does not deserve our respect,” said Abu Jundal, whose comrades have been firing crude but occasionally deadly rockets at Israeli towns for years. “They will pay a high price for their crimes,” he said, adding that morale was high among his men.

The overall commander of Hamas's armed wing said yesterday that close combat had occurred in some sectors of the front, which now snakes around the outskirts of Gaza City and down to Khan Younis, a large city in the south.

Abu Obeida, head of the Izz al-Din al-Qassam Brigades, said that his fighters had ambushed a unit of undercover Israeli soldiers trying to infiltrate deep into the strip, hitting them with mortar shells and a buried landmine weighing 100lb.

He said that another Israeli unit had entered a house with Hamas fighters inside, one of whom had blown himself up with a suicide bomb.

“We have hundreds of suicide bombers waiting for the Israelis, whose options are limited to either be killed, wounded or captured,” he said in a telephone interview with al-Jazeera, the Arabic television news channel.

Times Recommends

• Michael Jackson: Not the final chapter
• Indian Army spends10m rupees on golf buggies
• Brüno toned down for 15 rating