Though the pace of the advance by US-led forces was increasing, British Prime Minister Tony Blair believes "there will be many more difficulties to overcome," a spokesman for his office said.

British tanks rolled into the centre of Basra on Sunday and surrounded the local Baath Party headquarters, effectively taking control of Iraq's southern metropolis, military officials in the Gulf said.

A correspondent for the Qatar-based Arabic satellite television station Al-Jazeera reported that 25 tanks and armoured cars were seen in the city centre.

"We continue to see a steady advance, which is continuing to gather pace," with the situation in Basra, southern Iraq, developing in favour of coalition forces, Blair's spokesman said.

The British troops would show caution and "advance at a pace that will preserve our security and minimise casualties," he said.

"Regrettably, there will continue to be losses, though of course we will try to restrict that as much as possible," the spokesman said.

Later Sunday the defence ministry announced that three British soldiers were killed in action during the major push into the centre of Basra.

The deaths take to 30 the number of British serviceman to die since the war began on March 20.

"A soldier was killed in action in Basra on 6 April. His next of kin have been informed," the defence ministry said in a statement.

"In a separate incident, two other soldiers were killed in action in Basra later the same day. Their families are being informed," the statement, on the defence ministry's web site, said.

A spokesman for the Irish Guards, who were involved in the incursion, said they had pushed forward into the city, destroying positions defended by the fedayeen and other militia groups.

The move came a day after US troops rode tanks deep into Baghdad, though British Defence Secretary Geoff Hoon warned that coalition forces might encounter similar difficulties in the capital as they had in Basra.

British troops had been camped on the outskirts of Iraq's second city for almost two weeks before Sunday's foray, wary of urban warfare.

"Baghdad may prove to offer the same kind of problems that Basra has, that is some resistance from the militia, but also a need to avoid significant civilian casualties," Hoon told BBC television.

But Britain, which wants the United Nations to play a central role in post-war Iraq, hopes only a "very small number" of its troops will still be in Iraq in six to nine months time, though it would depend on the security situation, Hoon said.

"We want to see British forces come home as soon as possible," after the initial period of reconstruction of Iraq, he said.

"What we are working towards, what the Americans are working towards is restoring Iraq to its own people," he said.

SPACE.WIRE