It is one of the world's most volatile borders, separating the Middle East's most bitter of enemies. Erez - the only pedestrian crossing into Israel for 1.4 million Palestinians crammed into the Gaza Strip - has been largely sealed off since Hamas' takeover last summer, leaving its residents in an increasingly desperate plight. But the rescue of one, dying, Palestinian baby at the concrete fortress last week threw a ray of light on a little-known humanitarian agreement between Israel and Gaza's Hamas-run health ministry, at a time when they are locked in a state of conflict.

In a delicate operation, which I witnessed, eight-day-old Mohammed Amin El-Taian was carried across no man's land on a stretcher at midday by a doctor from the Gazan ministry of health and handed to his counterpart from Magen David Adom (MDA), the Israeli equivalent of the Red Cross.

Mohammed - crippled by a chest infection, and heart and gastric problems - was then transferred along with his mother to the Dana specialist children's hospital in Tel Aviv, where he was to get the emergency treatment needed to save his life. If he had been left at the under-resourced Shifa Hospital in Gaza City, where he was born, Mohammed's chances of survival would have been extremely slim.

The decision to allow him to cross the border-fortress - at the point where Hamas snipers fired at Israeli soldiers only days before - is part of a little-known humanitarian deal between health officials of the two enemies, in which a small number of the neediest patients in Gaza given emergency treatment in Israel's more advanced hospitals.

Such co-operation is now almost the only dialogue taking place between Gaza-based Palestinians and Israelis, at a time when rocket attacks by Hamas - and bloody reprisals by Israel - dominate the headlines.

One Israeli medic told me that one of Hamas' border-guards at Gaza, known as Ahmed, had struck up a working relationship with his Israeli counterpart to ensure transfers such as that which saved little Mohammed could take place.

“We co-operate every day. He rings me in the middle of the night, he has my mobile number. Despite the situation, we work together,” the medic says. As a result, MDA claims that around five patients a week are transferred between the two camps.

Yet human-rights groups claim that Mohammed is one of the lucky ones, and that the successful implementation of this little-known agreement is rare. One such group, the Israeli branch of Physicians for Human Rights, last November lodged an application with the country's high court on behalf of 11 seriously ill Gazans, who it said were denied visas to leave the territory for undefined security reasons. And last May, Mohammed Ahmed Ibrahim Mansour, 23, a Palestinian from Gaza, died after waiting five days for an emergency medical permit that Israel had repeatedly denied on “security” grounds.

Further claims made by human-rights groups - denied by Israel - state that some needy Palestinians are having their applications revoked because they refuse to become agents for Israeli security forces.

In particular, the UN office for the co-ordination of humanitarian affairs cited the case of Bassam al-Wahidi, a 28-year-old journalist from the Gaza town of Rafah, who travelled to Erez requiring an eye operation. Al-Wahidi claimed that, once at the border, he was interrogated by Israeli agents, and asked to become an informer. After refusing, he was turned back and has failed to get the permit and treatment to save his eyesight. The Physicians for Human Rights group says that this practice has been reported before, and they have complained about it.

Israel says it helps the patients it can under the terms of the deal. However, it adds that it is restricted by legitimate security concerns at a time when Hamas-affiliated militants fire around a dozen rockets a day into the Jewish state's border towns of Sderot and Ashkelon, near to Erez. Hamas, which does not recognise the existence of Israel, also claimed responsibility for the shooting of eight students at a religious school in Jerusalem last week.

Israeli border guards at Erez also tightened restrictions after a recent Hamas-led co-ordinated breach against one of the two other Gaza borders, the Rafah crossing with Egypt, which led to Palestinians flooding over the border. Standing in no-man's land with baby Mohammed, Yonni Yogadovsky, of the Israeli MDA, said that the child's transfer showed a glimpse of Israeli-Palestinian co-operation that should provide some hope even at a time of conflict, in the region.

“Nobody talks about it, people only ever talk about the violence,” he says. “But this is an established procedure and people from the hospitals [in Gaza] and Hamas know about it.

“We are neighbours and it happens that we don't like each other very much. But when it comes to emergencies that save human lives, this is beyond political disputes.”

Despite doubts over how effectively this extraordinary agreement has been implemented, for baby Mohammed - being treated by his country's historical enemies - this smallest of compromises between the most bitter of foes is likely to have saved his life.

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