British police said they had arrested two men on Saturday as they stepped up their efforts to capture a suspected network behind the suicide bomber who killed 22 people in Manchester earlier this week.
Officers used a controlled explosion to gain entry to the address in the north of the city where the latest arrests were made. Detectives are now questioning 11 men over the attack by Salman Abedi at a pop concert in Manchester on Monday.
While Britain's most senior counter-terrorism officer said police were confident that they had made "immense" progress and had apprehended a "large part of the network", extra armed officers will be on duty across the country with security stepped up at some 1,300 events over the long holiday weekend.
Britain remains on its highest threat level of critical, meaning an attack is expected imminently, with the army backing up police and hospitals across the country have told staff to be ready for another incident.
The Times newspaper reported on Saturday that intelligence officers had identified 23,000 militant extremists living in Britain.
Earlier this week a source with knowledge of the matter told Reuters the security services were managing 500 active operations involving some 3,000 people who were thought to pose a threat.
However, Assistant Commissioner Mark Rowley, the UK police chief for counter-terrorism, advised people to be vigilant but to "go out as you planned and enjoy yourselves".
There are a number of high-profile events over the weekend including soccer cup finals in London and Glasgow, and the Great Manchester Run.
While police and politicians have praised communities in Manchester for their reaction to the bombing, Greater Manchester Police Chief Constable said there had been a rise in reported hate crimes, from an average of 28 to 56 incidents on Wednesday.
"We can't directly link these to the events of Monday night and are continuing to monitor the situation," he said.
Political campaigning for the June 8 national election which was suspended after the Manchester attack resumed on Friday with the bombing becoming a central feature.
The opposition Labour Party, emboldened by a rise in opinion polls, argued that Britain's foreign policy had increased the risk of attacks and criticized Conservative Prime Minister Theresa May for cutting spending on policing.
May said Labour leader Jeremy Corbyn was saying Britain was to blame for the bombing.
"I want to make one thing very clear to Jeremy Corbyn and to you, and it is that there can never, ever be an excuse for terrorism," she said at a summit of Group of Seven leaders in Sicily.
A poll on Thursday put May's Conservatives five points ahead of Labour suggesting a far tighter race than previously anticipated.