Wrapped in blankets to fend off the winter chill, families packed up goats, furniture and clothes, clogging roads with taxis, cars and tractors in a major exodus to safety, dodging roadside bombs planted to kill US and NATO troops.

“We left the area because lots of aircraft were flying over and lots of forces were moving back and forth,” Shir Ali Khan told AFP after reaching Lashkar Gar, the capital of southern province Helmand, with his 25 relatives.

War and battle are nothing new to the 80,000 people from Marjah, a fertile Helmand River valley in southern Afghanistan, one of the world's main sources of heroin and for eight years a major bastion of Taliban insurgents.

What the military calls “shaping operations” have been going on for weeks.

Residents have described gunbattles to a beat of planes and helicopters

bringing in men and supplies ahead of what is expected to be a bloody battle.

Taliban too are massing, gathering around the town and firing a constant barrage of missiles on the encamped foreign troops.

“Some people left the area six months ago, because military operations have been going on and the Taliban are so violent,” said Khan, adding: “There are still lots of people left who can't leave, who have nowhere to go.”Beneath pearl-grey skies in the midst of a rainy season, men wearing turbans told reporters on the highway they feared for their safety as Afghan, NATO and US troops massed ahead of an offensive expected within days.

Nad Ali resident Abdul Rehman, just arrived in Lashkar Gah, said: “These operations are nothing new for us. There has always been military operations going on in Nad Ali, we're used to it now.

“People are bit more concerned and worried about this operation as there are more Afghan and foreign soldiers around Nad Ali than usual,” he said.

Now concerns are growing for those left behind, exposed to the Taliban's reported violent control tactics and fearing bloodshed from what has been billed as the biggest offensive since the 2001 US-led invasion.

“There are Taliban in Marjah and I have not noticed any decrease in their movements to show they are deserting the place,” said Rehman.

“We are worried,” he added.

Marjah was planned and built partly by the US government in the 1950s as a model agricultural area irrigated by a network of canals.

Today, those canals criss-cross fields of opium poppies, which at this time of year are tall and green, not yet blooming red and not yet oozing the sap that will be processed into heroin and shipped across the world.

The region has been under direct control of the Taliban, who work in tandem with drug traffickers to force local people to grow poppies, since US Marines flushed them out of other parts of Helmand more than two years ago.

What should be the bread basket of Afghanistan is instead one of the world's richest sources of opium and heroin, earning billions of illicit dollars each year that help fund the increasingly vicious insurgency.

For 38-year-old Mohammad Basir Khan, heading to safety with his family, his biggest fear was the crude bombs that the Taliban have made a staple of their arsenal in the fight against government troops.

“We worry about lots of roadside bombs,” he said.

The area is expected to be laced with improvised explosive devices (IEDs), mostly planted by roadsides and detonated by remote-control, the biggest killer of foreign troops in Afghanistan but still managing to kill more civilians.