By Rob Taylor - OUTPOST NOLEN | Afghanistan (Reuters) –

The mission to clear explosive traps ringing a U.S. base in Afghanistan ended disastrously with one soldier wounded by a mine and several others hurt after their armored convoy hit a roadside bomb.

Outpost Nolen, a small disused mud-walled school in the middle of grape and pomegranate fields providing insurgents with perfect cover, has experienced some of the most intense fighting in Arghandab district, a key Taliban insurgency route on the way to Kandahar city.

It is in the heart of the Taliban's spiritual home, and typical of the area the 150-000 strong NATO-led International Security Assistance Force (ISAF) must first secure for any hope of official governance or development to arrive.

A soldier brought in to help clear the area around the base was evacuated by medical helicopter after he stepped on an anti-personnel mine hidden by a gate in a deserted village used by Taliban fighters.

The still unidentified soldier was on his first clearance mission at Nolen, where several soldiers of the 2nd Brigade Combat Team of the U.S. 101st Airborne Division have been hit by Improvised Explosive Devices (IEDs), some losing limbs.

"We'd all walked right past it, we'd all stepped over the bitch. It happened when we were backtracking over it," said Sgt. Hunter Wilkie.

The blast triggered sporadic clashes, with insurgents firing a rocket propelled grenade (RPG) at the base, and U.S. helicopter gunships firing rockets and machineguns in reply at suspected Taliban positions in Charqulba village.

The outpost was set up as a base for patrolling in the area, which military commanders believe is used also to cache weapons and smuggle them on to Kandahar, but the village and walled fields are now a fire base for insurgents.

The lead armored truck in a supply and explosives disposal convoy was lucky to escape another insurgent RPG which was fired as it left the base and exploded in a nearby grape field.

But the same vehicle shortly afterwards struck an IED estimated at around 25 kg (55 pounds) buried at the end of a small stone irrigation canal bridge. The blast hurled it into the air and triggered a fire that eventually engulfed it.

The four passengers in the all-terrain MATV, built to resist roadside bombs, escaped with relatively minor injuries. But the blast set off another clash in which U.S. soldiers fired mortars at Charqulba.

"These guys were so lucky. In this instance, the vehicle worked," said explosives expert Staff Sergeant Craig Cohen, 27, from Fort Campbell.

The fighting highlights the difficulty U.S. and NATO troops have had in countering the bomb threat in Kandahar, despite shipping more than $3 billion worth of counter-IED technology to Afghanistan.

Insurgents have been making bombs with difficult to detect plastics and wood casings and the area around Nolen has been particularly heavily seeded.

While the bombs are smaller than the armored vehicle breaking bombs favored by Iraq insurgents, their use reached a high across Afghanistan in late June with more than 300 exploded or located, up from about 50 a week in mid-2007.

(Editing by David Fox and Ron Popeski)