Anti-terror police forced their way into a flat and shattered the door frame as they raided an address believed to belong to one of the attackers on a Greenwich housing estate.
They also raided an address in Saxilby, Lincolnshire in connection with the attack.
"We can confirm that the Metropolitan Police executed a search warrant under PACE (Police and Criminal Evidence Act) at an address in Lincolnshire," Lincolnshire police said.
Local media said addresses in the London area were also being searched by police. Scotland Yard, however, refused to comment, the reports said.
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Meanwhile, British Prime Minister David Cameron, who cut short his visit to Paris, has described the terror attack as "deeply shocking" that has "sickened us all".
"It was an attack on Britain and it was also a betrayal of Islam. There is nothing in Islam that justifies this truly dreadful act," he said, addressing the media outside 10 Downing Street here today, soon after he chaired an emergency meeting of the high-level COBRA crisis group.
The hour-long meeting of COBRA, which stands for Cabinet Office Briefing Room A and is the UK's highest crisis response group, was convened after the two extremists butchered a soldier in Woolwich, south-east London, yesterday.
It was attended by senior Cabinet ministers, police and intelligence chiefs to take stock of the security situation in the country.