A second British soldier has been killed in combat as British commanders declare Iraq's second city Basra a "military objective" in the light of fierce resistance.
There has been surprise resistance to coalition forces in Basra
British military spokesman Group Captain Al Lockwood said they were meeting resistance from irregulars, members of the Fedayeen, who were extremely loyal to Saddam Hussein's regime.
Several sandstorms were severely hampering operations on Tuesday.
Colonel Chris Vernon, a British forces spokesman in Kuwait, said UK troops were moving into the outskirts of the city to carry out "surgical" attacks on political and military targets.
He said they were also seizing "fleeting opportunities" to hit Iraqi tanks and artillery on the outskirts.
But the city itself was not a target and care was being taken to avoid harming residents, with the aim merely to prise the city from the grasp of the political regime and allow humanitarian aid in, he added.
UK FORCES IN IRAQ AT-A-GLANCE
UK commanders say southern city of Basra is an 'objective' after meeting resistance
Tank battle south of Basra, as about 35 Iraqi vehicles including tanks try apparent counter-attack on al-Faw peninsula
Port town of Umm Qasr now 'safe and open'
Raids overnight on Baath party buildings in al-Zubayr, near Basra
Number of UK dead and missing reach 20
Operations held up by sandstorms and thunderstorms
The second British combat fatality, who has not been named, died near the town of al-Zubayr, about 15 miles (24km) south-west of Basra.
The soldier, from the 1st Battalion The Black Watch, was killed in action on Monday night.
British forces south of Basra, meanwhile, have blocked an attempted breakout by up to 35 Iraqi vehicles, including tanks, seeking to press southward.
Military sources told the BBC British light tanks, helped by small helicopter gunships and surveillance helicopters, had destroyed about 20 of the Iraqi vehicles.
It is thought they could have been trying to re-take the al-Faw oil peninsula, which British marines have been holding for several days.
But many operations have been held up amid fierce sandstorms in Iraq and rain in Kuwait, which make it too dangerous to fly helicopters and reduce tank sight visibility.
The BBC's Paul Adams, in Qatar, says there is anxiety among the troops that the bad weather is encouraging Iraq snipers to approach convoys.
The southern Iraqi port of Umm Qasr is now secure after pockets of resistance were overcome, Group Captain Lockwood said.
He told the BBC humanitarian shipments could flow through the town within about 48 hours, once mines were cleared from the waters.
Elsewhere, several hundred British Royal Marines have been deployed along Iraq's southern border with Iran, amid concerns fighters there could try to exploit uncertainty caused by the war.
Coalition forces continue their advance on Baghdad, with some troops now less than 100 kilometres (60 miles) from the city.
In Basra on Monday night, lightning raids on two Baath party offices saw one official captured in a move to "delink the oppressive structure from the people", said British spokesman Colonel Vernon.
In other developments:
Prime Minister Tony Blair says "a huge amount" has been achieved by coalition forces
Two British soldiers injured in battle - one Royal Marine Glenn McCoy from Donnington in Telford, the other unnamed - have been flown to Birmingham's Selly Oak hospital for treatment. Their condition is unknown
An ICM poll for the Guardian newspaper shows 54% of people questioned said they approved of attacking Iraq to remove Saddam Hussein, with 30% against
UK commander Group Captain Mike Harwood warned that the Iraqi air force could be planning a surprise chemical attack