British troops have arrested several Iraqis suspected of plotting a bombing campaign ahead of Sunday's election.
British troops are on high alert ahead of the Iraqi election
The operation on Friday involved Iraqi special forces and 200 Scots Guards in raids on four houses in Basra.
The alleged large-scale bomb campaign was thought to have been aimed at polling stations and coalition troops based in the southern city.
On Saturday, Iraqi expats living in the UK will continue to cast their votes in the country's landmark elections.
The UK troops came under fire as they raided one house, about 150 yards from a polling station. There were no casualties.
Scots Guards commanding officer Lt Col Harry Nickerson said information suggested there were four insurgents, or insurgent groups, who were keen to disrupt the election.
A decision was taken to arrest them and search their homes.
"They want to bomb the polling stations or put large bombs into places to disrupt the process," he said ahead of the operation.
"We want to get to them before they get the chance."
The decision was taken to launch the raids, in an attempt to prevent potential widespread loss of life.
Soldiers from the Scots Guards left their Shaibah base south-west of Basra shortly after 6pm local time on Friday.
Lt Col Nickerson said he believed the operation had the support of the majority of Basra's population, although there would be a small minority who might object.
British commanders opted for a softly-softly approach to the raid in the hope of maintaining the element of surprise and minimising any adverse public reactions.
The raids took place during the night curfew imposed by the interim Iraqi government in the run up to the elections.
Two units from the new Iraqi army's elite tactical support unit led the raid, supported by two companies of the Scots Guards in Land Rovers.
Elsewhere in Iraq on Friday, insurgents attacked US troops, polling stations and Iraqi forces as security was tightened ahead of the election.
This report was pooled copy from Gethin Chamberlain of The Scotsman.