By Rosalind Russell

Basra - After a two-week siege, British tanks shot their way into the centre of Basra on Sunday in an attempt to stamp out dogged resistance in Iraq's second city from paramilitary fighters loyal to President Saddam Hussein.

British officers confirmed reports by Iraqi civilians leaving the city that a column of tanks and armoured personnel carriers had reached Baghdad Street running through the centre of Basra, Iraq's main southern city close to the Gulf coast.

"It's a town we clearly have got to get into and we've got to finally eradicate the ruling Baath Party and the irregulars who are operating in there," British military spokesperson Chris Vernon told BBC television.

"We are doing it with tanks that can take enemy small arms fire and with our infantry," Vernon said, adding that the British had seized a moment of opportunity after receiving information from residents on the whereabouts of Baathists.

Troops of the Irish Guards and Royal Scots Dragoons Guards had set off at dawn from a base near a bridge on the southern edge of Basra in 14 tanks and 14 Warrior armoured personnel carriers, Irish Guards Captain Alex Cosby told Reuters.

They advanced four kilometres to a roundabout Cosby described as the gates of Basra before pushing on. Residents later reported seeing 10 tanks about two kilometres further into the city.

It was not immediately clear whether the British forces intended to establish a permanent presence in central Basra or withdraw again after raiding their targets.

In early afternoon, this correspondent saw 15 tanks and troop carriers returning to their base near the bridge. But 15 Challenger tanks later left the base heading towards the city.

British officers and Basra residents said the British column had met fire from Iraqi Fedayeen paramilitaries in Basra and along the main road leading up to the city from shanty towns on the outskirts.

"We met resistance but a lot has been destroyed. We have destroyed some armour and we are now engaging bunker positions," Cosby said at one point.

British and United States forces have been encircling Basra since soon after invading Iraq from the south on March 20. They have so far held back from trying to storm Basra, saying they want to avoid major civilian casualties.

At the US and British central command in Qatar, a British military spokesperson said the aim was to set up checkpoints within the city boundaries "to reassure the population that we are coming to liberate them".

"There's still a fair way to go but this is another step forward," Group Captain Al Lockwood told Reuters.

British and US officials had hoped the Shi'ite Muslim people of Basra, who have no love for Saddam, a Sunni, would rise up of their own accord against Baghdad.

But Iraq's southern Shi'ites have bitter memories of doing just that after the 1991 Gulf War and being brutally suppressed by Saddam's forces after getting no help from the United States and its allies.

There have been persistent reports of Baathists intimidating Basra residents during the latest war. On Sunday, pro-Saddam militiamen with AK-47 assault rifles opened fire on private vehicles in an attempt to force civilians to fight British and US troops, witnesses said.

As this correspondent drove towards central Basra behind the British column, half a British dozen tanks could be seen along the road with their barrels pointing down side streets where commanders believed Iraqi militiamen had been hiding.

Spent 50-millimetre tank shells were lying around. There were signs of people looting factories in what appeared to be a mixed residential and industrial area.

A mystery that US and British forces are hoping to solve in Basra is the fate of Saddam's cousin and confidant Ali Hassan al-Majid, "Chemical Ali" - who organised the use of poison gas against Kurdish villagers in 1988.

The US military said on Sunday it had found the body of Ali's bodyguard in a house that was bombed in Basra on Saturday but could not confirm the fate of Ali himself. Iraq denied he had been hit.