In a week when gaza was gripped by a new wave of tension and bloody violence, we hear from two very different eyewitnesses: meet the rocket maker and the human rights worker. By Ed O'Loughlin.

The Popular Resistance Committees is a close ally of Hamas in the Gaza Strip. "Abed", a 28-year-old father of two, is one of the PRC's senior artificers, responsible for devising mines and designing and building rockets and mortars. It was with some surprise, therefore, that he started receiving phone calls from an Israeli spy.

"I was home two weeks ago, getting ready for evening prayers, sitting with my wife and child, and suddenly my mobile starting ringing. He said, I'm Rami, I'm from Shabak the Israeli security agency Shin Bet and I'm responsible for your area. What are you doing? I guess you're with your wife and your two children?' I said no, and he said Yes, your two children are with you, but now you've just moved out of the room'. I said, what do you want? He said If you don't stop your rockets it's only a matter of time before you are targeted'."

Anyone who has ever seen a modern spy movie knows what you're supposed to do next: hurl the phone as far as you can and then dive from the building before it or the telephone explodes. Next, go underground, and never use a phone or a computer again. Abed, on the other hand, merely hung up the phone. Half an hour later he was again nonplussed when Rami called back to continue the chat. "He threatened me again that we have our own ways to reach you, but the rockets we will use to assassinate you will be stronger than before.'"

Other members of the Popular Resistance Committee reported receiving threatening phone calls - an interesting insight into Israel's capacity to use mobile telephone networks to monitor and, in this case, harass its enemies. But the reaction of Abed and his comrades to their calls from Shin Bet illustrates another aspect of the conflict: the remarkable operational naivety which is often displayed by Palestinian militants, even after scores have already been assassinated by Israel.

"After that I realised that when talking on the phone that someone was listening to me," muses Abed.

"I changed the SIM card, but it seems like they were following the sound of my voice, because even after changing the SIM card I could hear someone was listening. My brother borrowed my mobile, and when he was talking to his friend someone else was talking to him on the same line."

It seems that Abed and his fellow militants do not know that when a mobile phone is connected to a network it identifies itself not only by its SIM card but also with the handset's own unique code. To foil detection it is necessary to change both SIM and telephone, not the SIM card alone.

And once snoopers know what phone you are using, it is a simple matter for them to fix your position. The phone in your pocket can also be turned into a highly effective bugging device - perhaps even a homing beacon for air-launched missiles. Abed and his fellow militants may be at a disadvantage to the average British 12-year-old when it comes to understanding modern urban warfare, but the rockets they make are still deadly enough. Ten days ago a 47-year-old resident of the border town of Sderot became the 12th Israeli to be killed by home-made rockets manufactured and fired from Gaza by the PRC, Islamic Jihad, Hamas, Fatah and other smaller groups.

The rocket that killed him was part of an escalated barrage fired by Hamas and its allies in revenge for Israel's assassination that same day of five senior Hamas militants. The resulting round of attrition, including a bloody Israeli ground raid, claimed the lives of more than 120 Palestinians - at least half of them civilians, 28 of them children - plus three Israeli soldiers killed in action and eight youths who were shot dead in Thursday's terror attack on a far-right Jewish religious institution in Jerusalem.

During this latest surge in killing, the Gaza militants succeeded for the first time in launching missiles more than 10 miles, into the centre of Ashkelon, an Israeli city of 110,000 inhabitants which was previously believed to be out of range.

As often before, Israel's security establishment attributed the assault on Ashkelon to new, advanced weapons, including modern anti-tank and anti-aircraft missiles, which the Palestinians are alleged to have obtained from Iran.

And also as before, no such weapons were employed by the Palestinian militants during their ineffectual attempts to resist last weekend's tank invasion.

According to Abed, the rockets that struck Askhelon were not the Soviet-designed Katyusha or Grad rockets spoken of in the Israeli media (there is, in fact, no such thing as a Grad missile) but were designed and built by himself and other militant artificers. "The new rockets are neither Grads nor Katyus has - they are home-made," he claims. "I myself am producing a 17km rocket and I'm working on one that will go 45km The real trouble is the cost. The new 45km rockets will cost $7000 each (£3500) to build. They'll need equipment and chemicals for the fuel that are hard to get. The ones that hit Ashkelon only cost about 2500 shekels (£350)."

The most commonly-fired missiles, generically referred to as "Qassams" after Hamas's armed wing, the Qassam Brigades, have a range of up to six miles, he says, and cost 1500 shekels (£205) each to make.

Since the present uprising began more than seven years ago around 4000 Palestinian missiles, mostly Qassams and home-made mortars, have been fired into Israel or its former Gaza settlements and military bases, part of a cycle of bombardment, blockade and invasion which has proved far more injurious to Gaza than to Israel.

Abed gave his interview last week at night while the latest bloody Israeli invasion, dubbed Operation Hot Winter, was still claiming militant and civilian lives in the battered northeastern fringes of Gaza City.

In the interests of security, he asked to be collected in a taxi from a street corner only a few hundred metres from the Israeli-controlled area, where explosions and gunfire were still disturbing the night.

At his direction the taxi lurched back and forth around the neighbourhood for the next half an hour, pulling occasional U-turns in the blacked-out, frightened streets, while Israeli drone aircraft - themselves equipped with missiles used for deadly air strikes - circled immediately overhead. On his own initiative, the driver kept switching his headlights off, apparently believing that this would make his slowly-meandering vehicle look less suspicious to snipers and drone operators hunting militants in the night.

It was with considerable relief that Abed's interviewers finally heard him reach the end of his story.

"I don't carry the mobile at all any more," he said regretfully.