The UK terrorism threat level has been reduced from critical to severe, Prime Minister Theresa May has said.
The change indicates an attack is highly likely, not imminently expected.
Soldiers deployed to support the police will be stood down on Monday night, at the close of the bank holiday weekend.
Earlier on Saturday, police evacuated an area of Moss Side in Manchester, in a search linked to Monday’s bomb attack at the Manchester Arena which killed 22 people and left scores injured.
The evacuation was described by Greater Manchester Police as a precautionary measure to “ensure everyone’s safety”.
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Mrs May made the announcement after leading a meeting of the government’s emergency committee Cobra on Saturday morning.
She said significant activity by the police during the last 24 hours had led to the threat being reduced.
It had been set at critical in the aftermath of the bombing.
Police make arrests
Detectives are questioning 11 men over the attack after a series of raids.
In the latest arrests, police held two men, aged 20 and 22, after carrying out a controlled explosion at an address in the Cheetham Hill area of Manchester early on Saturday.
There were also searches at a separate property in Cheetham Hill and in the Longsight area.
At the start of the bank holiday weekend, armed police are guarding hundreds of events across the UK
Senior officers have encouraged people to go out, but to remain vigilant.
Security is being increased at football and rugby finals, entertainment events and the Great Manchester Run.
Seven children were among those who died when Salman Abedi, 22, detonated a bomb at the Manchester Arena on Monday night, at the end of a concert by US singer Ariana Grande.
A total of 66 people remain in hospital, with 23 in critical care.