The skies above Fallujah burned red late on Monday as artillery, war planes and tanks pounded the Iraqi rebel bastion with a barrage of firepower at the start of an operation to retake the city. Following a day of heavy shelling and missiles, US marines and soldiers stormed the northern entrance to the city west of Baghdad as plane and tank fire lit up the night sky as Operation Phantom Fury got underway.
A unit of marines penetrated the insurgent heartland of the city barely an hour after the offensive started, bursting into the notorious Jolan district in the north-west with a blistering volley of heavy gunfire.
A separate unit also took control of Fallujah's train station in the north-east, a marine officer told AFP.
Inside the battle-scarred city missiles rained down indiscriminately, with the action most intense in the Askari district in the north-east and Jughaitha in the north, another AFP correspondent said.
The onslaught was unleashed after Allawi announced he had given the permission for the military to retake the city, the symbol of the potent insurgency that is bent on undermining his US-backed interim government.
And his defence minister warned that it was only a taste of what was to come, saying the major operation to retake the city would begin on Tuesday.
"Your job is to arrest the killers but if you kill them then let it be," Allawi said as he visited his soldiers at Camp Fallujah.
"You need to avenge the victims of the terrorists like the 37 children who were killed in Baghdad and the 49 of your colleagues who were slaughtered," he said, referring to two of the deadliest attacks unleashed by insurgents loyal to Iraq's most wanted militant and al Qaeda frontman Abu Musab al-Zarqawi.
In Washington, a defence official said about 12,000 US and Iraqi forces were taking part in the offensive.
In April, US marines withdrew from Fallujah after an assault on the city and reports of heavy civilian casualties sparked more widespread resistance in Iraq and drew widespread condemnation in the Arab world.
"The assault was launched today... Fallujah is completely surrounded and under siege," Iraqi Defence Minister Sheikh Hazem Shaalan told reporters in Baghdad.
"Tomorrow is the large-scale operation to retake the city," he added. "We've called it Operation Dawn. God willing, it's going to be a new, happy dawn for the people of Fallujah."
Up to 90 percent of Fallujah's 300,000-strong population is already thought to have fled the city.
Attempts to broker a peaceful solution between Baghdad and local leaders collapsed last month after Allawi threatened Fallujah with invasion if they did not surrender militants such as Zarqawi, whose followers have been behind some of the deadliest attacks and the beheading of hostages.
US and Iraqi officials believe the Jordanian-born Zarqawi, who has a 25 million dollar price on his head, has turned Fallujah into his main operating base, but residents deny this is the case.
Earlier on Monday, black smoke plumed above the western fringe of Fallujah, where US and Iraqi forces had seized the main hospital and two bridges in their first major foray into the city.
Violence around the western edge alone left 38 insurgents dead, Allawi said.
He imposed an indefinite curfew from 6:00pm on Fallujah, saying it would be lifted on an area-by-area basis as it was brought under government control.
At least 12 people were killed and more than 20 wounded in the overnight bombardments, said an official from a local clinic. The marines and Iraqi special forces met minimal resistance when they took control of the hospital and two bridges. But that changed within hours as they were forced to fight for the territory, using helicopters, planes and tanks, a pool reporter said. Edging closer to Jolan earlier, at least four 2,000-pound (900-kilogram) bombs were dropped in the north-west of the city, an AFP reporter said.
Marines poured into a complex of several buildings, including two apartment blocks, a school, a mosque and a government building, in the sector.
A total of about 20,000 US and Iraqi troops have been massing around Fallujah since mid-October.
The offensive erupted a day after the government declared a state of emergency across most of Iraq, with emergency measures slapped Monday on Fallujah and its sister restive hub of Ramadi.
US commanders estimate that 2,000 to 2,500 fighters, some loyal Zarqawi, are inside the city and its surrounding areas, ready to fight. The military believes that another 10,000 men could join in the battle.
Arab states appealed on Monday for both sides to spare civilian lives in the brewing bloody showdown.