A US gunship crew was cleared to attack two insurgents on the ground even though the pilots had reported that the men were trying to surrender, the leaked Iraq war logs reveal.

The Apache helicopter pilots killed both Iraqi men after being advised by a US military lawyer that they could not surrender to an aircraft and therefore remained valid targets. A leading military law expert consulted by the Guardian has questioned this legal advice.

The Guardian can also reveal that the helicopter involved in the incident in 2007 had the same call sign – Crazyhorse 18 – as the Apache whose crew later mistakenly killed two Reuters journalists and injured two children in a notorious shooting in urban Baghdad. The killings drew worldwide condemnation in April this year when WikiLeaks obtained video footage taken from the helicopter's gun camera and released it on the internet.

It has not been possible to establish whether the same personnel were involved in both attacks.

According to the account of the earlier incident in the leaked logs, the insurgents had jumped out of their truck after it came under fire from the Apache. "They came out wanting to surrender," Crazyhorse 18 signalled.

Clearance to kill came back from an unnamed lawyer at the nearby Taji airbase. "Lawyer states they can not surrender to aircraft and are still valid targets," the log entry says.

After receiving the lawyer's advice, the pilots reported that the men had by now got back into their truck and were attempting to drive on. The gunship made two attempts to kill the fleeing men, launching a Hellfire missile at the truck.

At first the fresh attack failed. "Individuals have run into another shack," the crew signalled. As the Apache hovered high in the sky, a few miles north of Baghdad, the pilots viewed a zoomed-in image of the fleeing pair on their video screen.

The crew then received a further specific top-level kill instruction from brigade HQ and made another strafing run, firing bursts from long distance at 300 rounds a minute from the Apache's 30mm cannon. This time, the gunner succeeded in killing both men.

At 1.03pm on 22 February, just 24 minutes after receiving legal clearance, the crew filed a log entry: "Crazyhorse 18 reports engaged and destroyed shack with 2X AIF [anti-Iraq forces]. Battle damage assessment is shack/dump truck destroyed."

Crazyhorse 18 was part of the US army's 1st Battalion, 227th Aviation Regiment, normally based at Fort Hood, Texas. Five months after this incident, on 12 July 2007, the crew of an Apache with the same call sign mistakenly killed 22-year-old Reuters photographer Namir Noor-Eldeen and his driver, Saeed Chmagh, after opening fire on a group of eight men they believed to be insurgents armed with rocket-propelled grenades and AK47 rifles in a Baghdad suburb.

Two children were badly injured and their father killed when the Apache crew fired armour-piercing shells at a van which arrived on the scene.

The account of the February incident recorded in the classified log suggests the Crazyhorse 18 crew were not trigger-happy, but sought immediate advice from their superiors at all stages of the attack.

Under the 1907 Hague regulations, it is forbidden "to kill or wound an enemy who, having laid down his arms, or having no longer means of defence, has surrendered at discretion".

Britain's own official Ministry of Defence publication, the Manual of the Law of Armed Conflict, says there are practical difficulties around surrenders to aircraft, but adds: "With the advent of close-support and ground-attack helicopter units, the surrender of ground troops … has become a more practical proposition."

One of Britain's foremost experts on the subject, Professor Sir Adam Roberts, cast doubt on the legal advice given to the Crazyhorse 18 crew. "Surrender is not always a simple matter," Roberts, emeritus professor of international relations at Oxford University and joint editor of Documents on the Laws of War, told the Guardian. But the reasoning given by the US military lawyer was "dogmatic and wrong".

"The issue is not that ground forces simply cannot surrender to aircraft," he said. "The issue is that ground forces in such circumstances need to surrender in ways that are clear and unequivocal."

However, he added: "If the insurgents did indeed get back into the truck and drove off in the same direction as previously, then they probably acted unwisely, in a way that called into question their act of surrender … The US airmen might legitimately reckon that the truck contained weapons and that the men could be intending to rejoin the fight sooner or later."

The detailed account of events on that February morning begins with a common occurrence: insurgents near the huge Taji airbase start lobbing rockets and mortar shells, in the hope of killing Americans. US troops return the shelling, and Crazyhorse 18 is dispatched on a mission to see whether the retaliation has had any effect. At 11.34am, three minutes after takeoff, the crew spot the insurgents fleeing their launch site with a mortar and tripod on the back of a Bongo – a light truck manufactured by Kia.

The crew confirm a "positive identification" of the enemy. But it is 13 minutes before the pilots are officially "cleared to engage" with automatic cannonfire by their headquarters.

The Apache opens fire, and two Iraqis fling themselves out of the Bongo as the heavy shells blast the truck and cause its stock of mortar ammunition to "cook off".

The enemy gunners try to make their escape in a dumper truck, driving northwards. At 12.33pm, the Apache reports that it has fired on the truck, "and then they came out wanting to surrender".

Two minutes later, "Crazyhorse 18 reports they got back into truck and are heading north". Four minutes after that: "Crazyhorse 18 cleared to engage dumptruck. 1/227 [1st Battalion, 227th Aviation Regiment] lawyer states they cannot surrender to aircraft and are still valid targets."

The two Iraqis try to take refuge in a shack. After a 13-minute delay, another instruction appears to come from a remarkably high level: the office of the commander [IH6] of the Ironhorse brigade at Camp Taji.

The signal reads: "IH6 approves Crazyhorse 18 to engage shack."

After the killing, the helicopter pilots summarise what for them and their superiors has apparently been a successful chase: "Ix engagement with 30mm. 2x AIF killed in action. 1x mortar system destroyed. 1x Bongo truck destroyed with many secondary explosions. 1x dumptruck destroyed. 1x shack destroyed."

At 1.25pm, their gunship heads home to Taji to refuel and reload with ammunition.