"WELCOME to Iraq from the fighting 61st. Have a nice day!"This gung-ho sign-off by embattled marines was the introduction into a hellish scene straight out of Dante.

"WELCOME to Iraq from the fighting 61st. Have a nice day!"

This gung-ho sign-off by embattled marines was the introduction into a hellish scene straight out of Dante.

Allied troops advancing into Iraq were clearly too late to stop departing Iraqi soldiers torching some oilfields in the south of the country before they could seize them intact.

Tracks from heavy armour criss-crossed the battlefield, obscured by the black smoke from detonated wellheads and fire trenches, pockmarked by futile defensive positions and littered with a few spent cartridges. There had clearly been a fight.

Driving into the scene of one of the first land attacks in the second Gulf war meant retracing the steps of US Marines who had stormed entrenched Iraqi positions – one barracks had been flattened into rubble.

Nine oil wells among the many hundreds in Iraq's largest oil-producing area of south Rumaila have been blazing since yesterday when US Marines launched the first wave of its ground assault from northern Kuwait.

Billowing clouds of black smoke greeted the British shock troops of 16 Air Assault Brigade as they crossed the border early this morning.

Passing one, I could feel the hot breath of as fire belched out, rippling out flames and tarry smoke

To the west American troops and heavy armour have ploughed across the western desert of Iraq, to the east the Desert Rats of 7th Armoured Brigade have linked up with US Marine tanks in a steady advance forward to the south west Royal Marines have secured the strategically important Al Faw peninsula.

But here on the centremost front – in Saddam Hussein's precious oilfields which can produce 2.9bn barrels a day – millions of dollars is today going up in thick, choking smoke, darkening the sky over the Kuwait-Iraq border in a chilling echo of the final stages of the first Gulf war when Saddam Hussein deliberately detonated Kuwait's northernmost wellheads.

Paras and infantrymen from the Royal Irish Regiment have gone in to secure oil installations in the hope that they can be speedily returned to service to bankroll the future rebuilding of a country that today is still in the throes of war.

A herd of camels that nonchalantly grazed around these sunburnt Ulsterman, picked around artillery guns with their barrels facing north – the position the coalition forces had directed Iraqi forces to adopt if they wanted to surrender.

Around 150 prisoners could be seen a short distance away.

With the quick pace that has characterised the war so far, Britain's newest rapid response brigade, which comprises two infantry battalions from the Royal Irish Regiment and 3 Parachute Regiment supported by light armoured vehicles of the Household Cavalry and helicopters from 3 Regiment, Army Air Corps, moved its 5,400 troops from their desert camp to relieve the US Marines regimental combat teams and conduct a 'mop up' operation in the heavily-mined area of south Rumaila.

Firefights were still raging today as the handover was completed, allowing the US Marine Corps' 5 Regimental Combat Team (RCT) to strike deeper into Iraq.

Meanwhile air attacks by coalition bombers and cruise missiles which have pummelled military targets such as gun emplacements, communications and command posts across Iraq in the first day of the air war proper that, in a surprising move, came two days after ground forces went in.

Waiting to move forward last night, flames from the fire trenches we now passed were clearly visible, casting an eery glow over the final staging post 11km from the breach where the brigade gathered before the thrust forward.

The oil installations are believed to have been widely booby-trapped by the Iraqis. Amid rumours circulating among British troops that Saddam Hussein has been killed in the first wave of cruise missile attacks, what remains of Iraq's high command is denying that they blew the wellheads.

Allied commanders are keen to locate the mainly immigrant oil workers who have fled the region. Over the past weeks these staff and soldiers on the ground have been the target of frequent leaflet drops and radio transmissions telling them to refrain from harming the oil infrastructure.

But demoralised defenders are known to be laced with officers from Saddam Hussein's loyal secret police and elite Republican Guard units in an effort to stiffen resolve.

The dangerous work of removing a multitude of mines and other deadly booby traps littering the oilfields has fallen to teams of Royal Engineers as the 1st Marine Division, who spearheaded a lightning strike around 1am local time on Friday, continue to push north.

Movement of defending Iraqi forces immediately north of the border are believed to have forced the hand of the coalition's military planners in bringing forward the ground attack.

According to Lt Colonel George Butler, of 3 Regiment, Army Air Corps, which provides vital air support to the brigade with Gazelle and Lynx helicopters, the oilfields and its seven gas and oil separation plants (GOSPS) were a key strategic target in the initial phases of the operation – and were to play a pivotal role in bankrolling the rebuilding of Iraq when the hostilities cease.

"The oil fields are key to this. We are doing everything we can to prevent ecological disaster and prevent whatever destruction we can."

Enemy resistance in the area has "in pockets" been fiercer than expected, said Captain Matt Willcock, spokesman for 3 Regiment, Army Air Corps.

But he added US Marines have made good progress in their advance taking only "light" casualties, mainly due to anti-personnel mines. One US officer has been confirmed killed. No British casualties have been reported in this area so far although elsewhere 15 British servicemen, including 8 Royal Marines, have been killed in two helicopter accidents.

Light damage has also been caused to roads and road infrastructure going through the oilfield area in south Rumaila.

There have been notable successes in the push forward across the 30km-wide front in the brigade's sector which extends 60km northwards of the border.

Two US-made Stinger surface-to-air missiles – similar to the type supplied to the Mujahadeen in Afghanistan – have been discovered in the area of operation in south Rumayla.

Coalition forces in the border area have been targeted by a long range surface-to-surface missile which although it fell short of its target and landed in Iraq, has been revealed as having a range of 350km – far in excess of the UN-sanctioned limit of 150km.

Further to the east, there have been reports of Iraqi tanks moving in the region of Basra, north of where British Royal Marine Commandos of 3 Commando Brigade have taken control of the Al Faw peninsula.

Challenger Mk2 tanks from 7th Armoured Brigade have managed to link up with the M1 Abrams tanks of US Marines' 7 Regimental Combat Team to engage the enemy after friendly-fire incident.

Unconfirmed reports say British and American forces have taken up to 1,000 prisoners in the war so far together. Significant collapses in the command structure have occurred with a number of prisoners including high-ranking officers.

A lieutenant-colonel from the ruling Ba'ath party and the commander and his second-in-command have been captured while only ten Iraqi military personnel are reported to have been killed.